Ediacaran microfossils from the Doushantuo Formation chert nodules in the Yangtze Gorges area, South China, and new biozones 9781119564195, 1119564190

Table of contents :
Title Page......Page 3
Contents......Page 4
Introduction......Page 7
General regional geology......Page 8
The Doushantuo Formation lithostratigraphy......Page 10
Depositional environments......Page 11
Age of the Doushantuo Formation......Page 12
Materials and methods......Page 13
Studied geological successions......Page 15
The Baiguoyuan section......Page 17
The Jiuqunao section (= Jijiawan)......Page 20
The Jiulongwan composite section......Page 25
The Chenjiayuanzi section......Page 27
The Wangfenggang section (= Liantuo)......Page 30
The Niuping composite section......Page 31
The northern Xiaofenghe section......Page 33
The southern Xiaofenghe section......Page 35
The Dishuiyan section......Page 36
General comments......Page 37
The Doushantuo Formation biostratigraphy......Page 38
Species recorded in member II......Page 39
Concurrent species in members II and III......Page 40
Species restricted to member III......Page 41
Establishing stratigraphic ranges of selected species......Page 42
New biozones in the Doushantuo Formation......Page 46
Tanarium pycnacanthum–Ceratosphaeridium glaberosum Assemblage Zone......Page 47
Conclusions......Page 48
Alicesphaeridium medusoidum Zang in Zang & Walter, 1992, emend. Grey, 2005......Page 49
Ancorosphaeridium magnum Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015......Page 52
Appendisphaera clustera n. sp.......Page 53
Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005......Page 54
Appendisphaera longispina Liu, Xiao, Yin, Chen, Zhou & Li, 2014......Page 60
Appendisphaera longitubulare (Liu, Xiao, Yin,Chen, Zhou & Li, 2014) n. comb.......Page 61
Appendisphaera setosa Liu, Xiao, Yin, Chen, Zhou & Li, 2014......Page 62
Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993, emended......Page 64
Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005......Page 67
Asseserium diversum Nagovitsin & Moczydłowska, 2012......Page 71
Genus Asterocapsoides Yin L. & Li, 1978, emend. Xiao, Zhou, Liu, Wang & Yuan, 2014......Page 72
Bacatisphaera sparga n. sp.......Page 74
Briareus borealis Knoll, 1992......Page 77
Briareus vasformis n. sp.......Page 79
Genus Cavaspina Moczydłowska, Vidal & Rudavskaya, 1993......Page 81
Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993......Page 82
Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993......Page 84
Cymatiosphaeroides forabilatus n. sp.......Page 87
Cymatiosphaeroides kullingii Knoll, 1984, emend. Butterfield, Knoll & Swett, 1994......Page 90
Genus Dicrospinasphaera Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended......Page 92
Dicrospinasphaera improcera n. sp.......Page 93
Dicrospinasphaera zhangii Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended......Page 95
Distosphaera? corniculata n. sp.......Page 97
Distosphaera speciosa Zhang, Yin, Xiao & Knoll, 1998, emended......Page 99
Eotylotopalla dactylos Zhang, Y., Yin L., Xiao & Knoll, 1998......Page 101
Eotylotopalla delicata Yin, L., 1987......Page 102
Eotylotopalla quadrata n. sp.......Page 103
Genus Ericiasphaera Vidal, 1990, emend. Grey, 2005......Page 105
Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1988......Page 107
Genus Estrella n. gen.......Page 110
Estrella greyae n. sp.......Page 112
Genus Gyalosphaeridium Zang in Zang & Walter, 1992, emend. Grey 2005......Page 114
Gyalosphaeridium pulchrum Zang in Zang & Walter, 1992, emend. Grey 2005......Page 117
Genus Hocosphaeridium Zang in Zang & Walter, 1992 emend. Xiao, Zhou, Liu, Wang & Yuan, 2014......Page 118
Hocosphaeridium anozos (Willman, 2008) Xiao, Zhou, Liu, Wang & Yuan, 2014......Page 119
Knollisphaeridium coniformum n. sp.......Page 121
Knollisphaeridium maximum (Yin, L., 1987) Willman & Moczydłowska, 2008, emended......Page 124
Genus Laminasphaera n. gen.......Page 129
Genus Membranosphaera n. gen.......Page 130
Genus Mengeosphaera Xiao, Zhou, Liu, Wang & Yuan, 2014......Page 133
Mengeosphaera chadianensis (Chen & Liu, 1986) Xiao, Zhou, Liu, Wang & Yuan, 2014......Page 135
Mengeosphaera gracilis Liu, Xiao, Yin, Chen, Zhou & Li, 2014......Page 138
Mengeosphaera latibasis Liu, Xiao, Yin, Chen, Zhou & Li, 2014, emended......Page 139
Mengeosphaera cf. M. stegosauriformis......Page 142
Multifronsphaeridium pelorium Zang in Zang & Walter, 1992, emend. Grey, 2005......Page 144
Sinosphaera speciosa (Zhou, Brasier & Xue, 2001) Xiao, Zhou, Liu, Wang & Yuan, 2014......Page 146
Tanarium capitatum n. sp.......Page 149
Tanarium cuspidatum Liu, Xiao, Yin, Chen, Zhou & Li, 2014, comb. nov., emended......Page 151
Tanarium muntense Grey, 2005......Page 153
Tanarium paucispinosum Grey, 2005......Page 155
Tanarium triangularis (Liu, Xiao, Yin, Chen, Zhou & Li, 2014) new combination......Page 157
Tanarium tuberosum Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2015......Page 159
Tanarium uniformum n. sp.......Page 162
Variomargosphaeridium litoschum Zang in Zang & Walter, 1992......Page 164
Verrucosphaera minima n. sp.......Page 166
Genus Weissiella Vorobeva, Sergeev & Knoll, 2009, emended......Page 168
Weissiella grandistella Vorobeva, Sergeev & Knoll, 2009, emended......Page 169
Acknowledgements......Page 172
References......Page 173
EULA......Page 179

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Ediacaran microfossils from the Doushantuo Formation chert nodules in the Yangtze Gorges area, South China, and new biozones by

Pengju Liu and Małgorzata Moczydłowska

Acknowledgements Financial support for the publication of this issue of Fossils and Strata was provided by the Lethaia Foundation

Contents Ediacaran microfossils from the Doushantuo Formation chert nodules in the Yangtze Gorges area, South China, and new biozones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Geological setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 General regional geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 The Doushantuo Formation lithostratigraphy . . . . . . . . . . . . . . 4 Depositional environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Age of the Doushantuo Formation. . . . . . . . . . . . . . . . . . . . . . . . 6 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Repository. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Studied geological successions . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 The Baiguoyuan section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 The Jiuqunao section (= Jijiawan). . . . . . . . . . . . . . . . . . . . . . . . 14 The Jiulongwan composite section . . . . . . . . . . . . . . . . . . . . . . . 19 The Chenjiayuanzi section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 The Nantuocun section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 The Wangfenggang section (= Liantuo) . . . . . . . . . . . . . . . . . . 24 The Niuping composite section. . . . . . . . . . . . . . . . . . . . . . . . . . 25 The northern Xiaofenghe section . . . . . . . . . . . . . . . . . . . . . . . . 27 The southern Xiaofenghe section . . . . . . . . . . . . . . . . . . . . . . . . 29 The Dishuiyan section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 The Liuhuiwan section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Biostratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 General comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 The Doushantuo Formation biostratigraphy . . . . . . . . . . . . . . 32 Species recorded in member II . . . . . . . . . . . . . . . . . . . . . 33 Concurrent species in members II and III . . . . . . . . . . . . 34 Species restricted to member III . . . . . . . . . . . . . . . . . . . . 35 Establishing stratigraphic ranges of selected species . . . . . . . . 36 New biozones in the Doushantuo Formation. . . . . . . . . . . . . . 40 Appendisphaera grandis–Weissiella grandistella– Tianzhushania spinosa Assemblage Zone . . . . . . . . . . . 41 Tanarium tuberosum–Schizofusa zangwenlongii Assemblage Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Tanarium conoideum–Cavaspina basiconica Assemblage Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Tanarium pycnacanthum–Ceratosphaeridium glaberosum Assemblage Zone . . . . . . . . . . . . . . . . . . . . . . 41 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Systematic palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Genus Alicesphaeridium Zang in Zang & Walter, 1992, emend. Grey, 2005 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Alicesphaeridium medusoidum Zang in Zang & Walter, 1992, emend. Grey, 2005 . . . . . . . . . . . . . . . . . . 43 Genus Ancorosphaeridium Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015 . . . . . . . . . 46 Ancorosphaeridium magnum Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015 . . . . . 46 Genus Appendisphaera Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005 . . . . . . . . 47 Appendisphaera clustera n. sp. . . . . . . . . . . . . . . . . . . . . . . 47 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005 . . . . . 48 Appendisphaera lemniscata n. sp. . . . . . . . . . . . . . . . . . . . 54 Appendisphaera longispina Liu, Xiao, Yin, Chen, Zhou & Li, 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Appendisphaera longitubulare (Liu, Xiao, Yin, Chen, Zhou & Li, 2014) n. comb. . . . . . . . . . . . . . . . . . . . . . . . 55 Appendisphaera setosa Liu, Xiao, Yin, Chen, Zhou & Li, 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993, emended . . . . . . . . . . . . . . . . . . . . . 58 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005 . . . . . 61 Genus Asseserium Nagovitsin & Moczydłowska, 2012 . . . . . 65 Asseserium diversum Nagovitsin & Moczydłowska, 2012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Asseserium fusulentum Nagovitsin & Moczydłowska, 2012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Genus Asterocapsoides Yin L. & Li, 1978, emend. Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . . . . . . . . . . . . . . 66

Asterocapsoides fluctuensis n. sp.. . . . . . . . . . . . . . . . . . . . . 68 Genus Bacatisphaera Zhou, Brasier & Xue, 2001, emend. Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . . . . . . . . . 68 Bacatisphaera sparga n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . 68 Genus Briareus Knoll, 1992 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Briareus borealis Knoll, 1992 . . . . . . . . . . . . . . . . . . . . . . . . 71 Briareus robustus n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Briareus vasformis n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Genus Calyxia Willman, 2008. . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Calyxia xandaros Willman, 2008 . . . . . . . . . . . . . . . . . . . . 75 Genus Cavaspina Moczydłowska, Vidal & Rudavskaya, 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993 . . . . . . . . . . . . . . . . . . . . . . . . 76 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Cavaspina conica n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Genus Cymatiosphaeroides Knoll, 1984, emend. Knoll, Swett & Mark, 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Cymatiosphaeroides forabilatus n. sp. . . . . . . . . . . . . . . . . 81 Cymatiosphaeroides kullingii Knoll, 1984, emend. Butterfield, Knoll & Swett, 1994 . . . . . . . . . . . . . . . . . . . 84 Genus Dicrospinasphaera Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended . . . . . . . 86 Dicrospinasphaera improcera n. sp. . . . . . . . . . . . . . . . . . . 87 Dicrospinasphaera zhangii Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Genus Distosphaera Zhang, Yin, Xiao & Knoll, 1998, emended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Distosphaera? corniculata n. sp. . . . . . . . . . . . . . . . . . . . . . 91 Distosphaera speciosa Zhang, Yin, Xiao & Knoll, 1998, emended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Genus Eotylotopalla Yin, 1987 . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Eotylotopalla dactylos Zhang, Y., Yin L., Xiao & Knoll, 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Eotylotopalla delicata Yin, L., 1987 . . . . . . . . . . . . . . . . . . 96 Eotylotopalla quadrata n. sp. . . . . . . . . . . . . . . . . . . . . . . . 97 Eotylotopalla strobilata (Faizullin, 1998) Sergeev, Knoll & Vorobeva, 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Genus Ericiasphaera Vidal, 1990, emend. Grey, 2005 . . . . . . . 99 Ericiasphaera fibrilla n. sp. . . . . . . . . . . . . . . . . . . . . . . . . 101 Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Ericiasphaera rigida Zhang, Yin, Xiao & Knoll, 1998 . . 104 Genus Estrella n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Estrella greyae n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Estrella recta n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Estrella sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Genus Gyalosphaeridium Zang in Zang & Walter, 1992, emend. Grey 2005 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Gyalosphaeridium pulchrum Zang in Zang & Walter, 1992, emend. Grey 2005 . . . . . . . . . . . . . . . . . . . . . . . . 111 Genus Hocosphaeridium Zang in Zang & Walter, 1992 emend. Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . 112 Hocosphaeridium anozos (Willman, 2008) Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . . . . . . . . . . . . . . . 113 Genus Knollisphaeridium Willman & Moczydłowska, 2008, emended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Knollisphaeridium bifurcatum Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Knollisphaeridium coniformum n. sp. . . . . . . . . . . . . . . . 115 Knollisphaeridium heliacum n. sp. . . . . . . . . . . . . . . . . . . 118 Knollisphaeridium maximum (Yin, L., 1987) Willman & Moczydłowska, 2008, emended . . . . . . . . . . . . . . . . . . 118 Genus Laminasphaera n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . 123 Laminasphaera capillata n. sp. . . . . . . . . . . . . . . . . . . . . . 124 Genus Membranosphaera n. gen. . . . . . . . . . . . . . . . . . . . . . . 124 Membranosphaera formosa n. sp. . . . . . . . . . . . . . . . . . . 127 Genus Mengeosphaera Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Mengeosphaera chadianensis (Chen & Liu, 1986) Xiao, Zhou, Liu, Wang & Yuan, 2014. . . . . . . . . . . . . . . . . . . 129 Mengeosphaera flammelata n. sp. . . . . . . . . . . . . . . . . . . 132

Mengeosphaera gracilis Liu, Xiao, Yin, Chen, Zhou & Li, 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Mengeosphaera latibasis Liu, Xiao, Yin, Chen, Zhou & Li, 2014, emended. . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Mengeosphaera lunula n. sp. . . . . . . . . . . . . . . . . . . . . . . . 136 Mengeosphaera cf. M. stegosauriformis . . . . . . . . . . . . . . 136 Genus Multifronsphaeridium Zang in Zang & Walter, 1992, emend. Grey, 2005 . . . . . . . . . . . . . . . . . . . . . 137 Multifronsphaeridium pelorium Zang in Zang & Walter, 1992, emend. Grey, 2005 . . . . . . . . . . . . . . . . . . . . . . . . 138 Multifronsphaeridium ramosum Nagovitsin & Moczydłowska in Moczydłowska & Nagovitsin, 2012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 Genus Sinosphaera Zhang, Yin, Xiao & Knoll, 1998 emend. Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . 140 Sinosphaera speciosa (Zhou, Brasier & Xue, 2001) Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . . . . . . . . . 140 Genus Tanarium Kolosova, 1991 emend. Moczydłowska, Vidal & Rudavskaya, 1993 . . . . . . . . . . . . 143 Tanarium capitatum n. sp. . . . . . . . . . . . . . . . . . . . . . . . . 143 Tanarium cuspidatum Liu, Xiao, Yin, Chen, Zhou & Li, 2014, comb. nov., emended . . . . . . . . . . . . . . . . . . . . . . 145 Tanarium minimum Liu, Xiao, Yin, Chen, Zhou & Li, 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Tanarium muntense Grey, 2005 . . . . . . . . . . . . . . . . . . . . 147 Tanarium paucispinosum Grey, 2005. . . . . . . . . . . . . . . . 149 Tanarium pilosiusculum Vorobeva, Sergeev & Knoll, 2009 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Tanarium triangularis (Liu, Xiao, Yin, Chen, Zhou & Li, 2014) new combination . . . . . . . . . . . . . . . . . . . . . . 151 Tanarium tuberosum Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2015. . . . 153 Tanarium uniformum n. sp. . . . . . . . . . . . . . . . . . . . . . . . 156 Genus Variomargosphaeridium Zang in Zang & Walter, 1992 emend. Xiao, Zhou, Liu, Wang & Yuan, 2014 . . . . . 158 Variomargosphaeridium litoschum Zang in Zang & Walter, 1992 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Variomargosphaeridium varietatum n. sp. . . . . . . . . . . . 160 Genus Verrcosphaera n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . 160 Verrucosphaera minima n. sp. . . . . . . . . . . . . . . . . . . . . . 160 Genus Weissiella Vorobeva, Sergeev & Knoll, 2009, emended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Weissiella grandistella Vorobeva, Sergeev & Knoll, 2009, emended. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Ediacaran microfossils from the Doushantuo Formation chert nodules in the Yangtze Gorges area, South China, and new biozones PENGJU LIU AND MAŁGORZATA MOCZYDŁOWSKA

Liu, P. & Moczydłowska, M. 2019: Ediacaran microfossils from the Doushantuo Formation chert nodules in the Yangtze Gorges area, South China, and new biozones. Fossils and Strata, No. 65, pp. 1–172. The new geological survey of the Ediacaran Doushantuo Formation and micropalaeontological studies have yielded a much larger and more diverse association of organic‐ walled microfossils than previously reported. Over 100 species recovered from chert nodules have now been identified, including 24 new species. The microfossil taxonomy has been revised accordingly, adding to the appreciation of biodiversity, global distribution and biostratigraphic significance. The species ranges have been scrutinized and the first and last appearance datum have been established for several worldwide distributed species that are used for proposed new assemblage zones in the Yangtze Gorges area, and potentially for global subdivision of the Ediacaran System. These are, in ascending stratigraphic order, the Appendisphaera grandis–Weissiella grandistella–Tianzhushania spinosa, Tanarium tuberosum–Schizofusa zangwenlongii, Tanarium conoideum–Cavaspina basiconica and Tanarium pycnacanthum–Ceratosphaeridium glaberosum Assemblage Zones. The successive zones’ lower boundaries are estimated at 633, 620, 610 and shortly after 580 Ma time horizons. The geological review of the Doushantuo Formation and new observations of eleven successions in an attempt to discern unconformities and stratigraphic hiati have recognized the relative time relationships between dismembered successions and have updated the species ranges. The Doushantuo Formation is sedimentologically discontinuous, partially condensed and comprises several un‐ and paraconformities involving hiati of unknown duration. Therefore, the species and zone ranges, with the exception of the two basal zones that are bracketed by isotopic datings, are approximate. The biotic radiations documented by microfossil appearance and the origin of new species at the very beginning of the Ediacaran Period at 633 Ma, followed exponentially through the interval up to 565 Ma (ca. 68 Ma) are innovative evolutionary events. Ediacaran microbiota phylogenetic affiliations are not fully resolved and assumed to be among auto‐ and heterotrophic protists or even metazoans. Many taxa are algal in origin, including those studied here. Biological affinities of microfossils remain among the most intriguing problems in the evolution of life at that time. □ Acritarchs, Ediacaran biozones, Ediacaran radiations, phytoplankton, taxonomy. Pengju Liu [[email protected]], Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; Małgorzata Moczydłowska [[email protected]], Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16 SE 752 36 Uppsala, Sweden; manuscript received on 2/11/2017; manuscript accepted on 10/07/ 2018.

Introduction The evolutionary history of the biosphere is intrinsically bound up with global environmental change from the primary formation of habitable conditions, increasing oxygenation through the Proterozoic Eon that made the Earth more suitable for organisms with complex metabolic processes and higher aerobic requirements, leading finally to a geosystem that could sustain animals. The terminal Proterozoic and its Ediacaran Period is a unique example of both environmental and biotic transformations leading to the

modern world. The recovery of marine basins and climatic rebound after the Cryogenian ice ages, global warming, epicontinental transgressions and increased nutrient input formed ecosystems in which bacteria, protists and multicellular eukaryotes, including emerging metazoans, rapidly evolved (Jenkins et al. 2004; Grey 2005; Narbonne 2005; Canfield et al. 2007; Grotzinger et al. 2011; Hoffman et al. 2017). These codependent relationships between the Ediacaran environmental and biotic systems are elegantly recorded by the wealth of organismal lineages and discrete taxa in the newly emergent marine niches.

DOI 10.1002/9781119564195 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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The exponential diversification of unicellular, organic‐walled microbes revealed in the number of new species, their morphologic disparity and the narrow time frame in which they appear, is well documented in the Ediacaran successions. Their number exceeds 100 described form‐species with worldwide distribution, of which some are endemic. The best known of them by morphologic complexity and variable preservation modes (organically preserved or permineralized) are microfossil assemblages from central and southern Australia, the Siberian and East European platforms, and South China. Their discovery and the early search for diversity and phylogenetic affinities (Timofeev 1969; Zhang 1981a, b; Yin 1985; Zang & Walter 1989, 1992a, b; Moczydłowska et al. 1993; Yuan & Hofmann 1998; Zhang et al. 1998a, b), and subsequent comprehensive studies (Grey 2005; Vorobeva et al. 2007, 2009a; Willman & Moczydłowska 2008, 2011; Sergeev et al. 2011; Moczydłowska & Nagovitsin 2012; Liu et al. 2014a, b; Xiao et al. 2014a), changed the concept of Precambrian life alongside the famous Ediacara‐type biota and early metazoans (Glaessner 1984; Narbonne 2005; Fedonkin et al. 2007; Vickers‐Rich & Komarower 2007). The Ediacaran environmental and biotic development is an affirming model for the theory of evolution by natural selection some 150 years after its formulation by Darwin (1859). The Ediacaran successions in the Yangtze Gorges area, part of the Yangtze Platform in South China, are comprised of carbonate and siliciclastic sedimentary rocks accumulated in shallow to more basinal marine depositional conditions (Jiang et al. 2011). They have been intensively studied because of the yield of a diverse early biota that is highly significant from an evolutionary point of view. The lower Ediacaran Doushantuo Formation in South China is overlain by the Dengying/Liuchapo formations and is of major interest because of its exceptional preservation of distinct microfossils (for recent summaries, see Liu et al. 2014b; Xiao et al. 2014a; Zhou et al. 2017a with references). The geochronology of the formation is well constrained from 635 to 551 Ma (Condon et al. 2005) and provides a time frame for the estimation of the rate of speciation and evolution of early biotas. The Doushantuo succession is a potential candidate for the subdivision of the Ediacaran System (Narbonne et al. 2012; Xiao et al. 2016). We examined eleven sections with exposures of the Doushantuo Formation in the Yangtze Gorges area (Fig. 1A, B) for organic‐walled microfossils in member II, and in certain intervals of member III, as a continuation of the detailed studies carried out by Liu et al. (2014b) on member III. Our focus was on the lower part of the Doushantuo Formation with

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the objective of revealing the appearances and earliest ranges of microfossil species for biostratigraphic application; testing the current biozones; and establishing new, refined biozones. The findings extend the known occurrence of many species, document numerous previously unknown species based on new material and revised taxonomy and include an attempt to formulate biozones suitable for the regional and global biostratigraphy and the Ediacaran System subdivision.

Geological setting General regional geology In a tectonic framework, the South China crustal block constitutes a major terrane of the present‐day continent. It was amalgamated about 1 Ga into a stable Proterozoic craton, including some Archaean 2.8 Ga basement, and subsequently covered by sedimentary successions of the Neoproterozoic and younger ages (Li et al. 2003; Wang & Li 2003; Torsvik & Cocks 2017). The Neoproterozoic sedimentary cover that overlies the Yangtze block consists of the two Cryogenian glaciogenic diamictites and intervening interglacial shale/siltstone/sandstone strata and the Ediacaran marine carbonate and siliciclastic deposits that extend over a large area of the Yangtze Platform (Zhou et al. 2004; Jiang et al. 2006, 2011; Dobrzinski and Bahlburg 2007; Fig. 1A, B). The Ediacaran successions on the Yangtze Platform reach a total cumulative thickness of ca. 400– 900 m (Xing et al. 1996) or ca. 250–1000 m (Jiang et al. 2011) and accumulated in shallow marine to basinal depositional settings (Zhu et al. 2003, 2013; Jiang et al. 2006, 2011; Zhou & Xiao 2007). They are well exposed across the platform area, although in different stratigraphic portions and in variable vertical and lateral occurrences that overlie the Nantuo Formation diamictite (Fig. 2). The strata are largely un‐deformed, other than dipping at a low angle and flexured along the faults. They have been strongly diagenetically altered by hydrothermal silicification, phosphatization and carbonate crystallization, although not metamorphosed (Derry 2010; Xiao et al. 2010; Derkowski et al. 2013; Hohl et al. 2015). The entire Ediacaran succession is relatively thin in comparison with other globally distributed successions. It is highly condensed or reduced in thickness, sedimentologically discontinuous and comprises regional unconformities and stratigraphic gaps whose extent are unknown (Wang et al. 1998; Zhu et al. 2003, 2007a, b, 2013; Grey 2005; Xiao et al. 2012; Fig. 2; see below). The Ediacaran strata are referred to the Doushantuo and the overlying Dengying/Liuchapo formations, which range in thickness

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 1. Geological sketch‐map of China showing the major crustal blocks (A) and the Huangling Anticline and Yangtze Gorges area with location of studied sections (B). The white frame in (A) marks the position of the Huangling Anticline in the northern Yangtze Platform. Modified after Liu et al. (2014b).

from 40 to 220 m and 200 to 1000 m, respectively (Zhang et al. 2005; Zhou et al. 2007; Zhu et al. 2007a, b, 2013; Jiang et al. 2011; Xiao et al. 2012; Liu et al. 2014b). The Doushantuo Formation is of a major interest because it contains evolutionarily novel and diverse fossil assemblages. It has been extensively studied in various aspects of its litho‐, chemo‐ and biostratigraphy, facies development and environmental conditions, and geochronology (Jiang et al. 2011; Zhu et al. 2013; Liu et al. 2014a, b; Xiao et al. 2014a, b; Zhou et al. 2017a, b; and references there). The formation’s geochronology is well‐established within ca. 635– 551 Ma (Condon et al. 2005), and while the entire time span of the Ediacaran Period is 635–541 Ma (Ogg et al. 2016), its terminal 10 Ma is encompassed on the Yangtze Platform by the Dengying Formation (Fig. 2). The Doushantuo and Dengying successions are among potential candidates for the Ediacaran System chronostratigraphic subdivision (Narbonne et al. 2012; Xiao et al. 2016). The type area of the Doushantuo Formation is around the Yangtze Gorges, and the type section (‘type locality’) is in the Tianjiayuanzi section (Zhao et al. 1985; Wang et al. 1998; Zhu et al. 2003; Lu et al. 2012), where it extends between the

Nantuo and Dengying formations and dips 7° to 11° (Zhao et al. 1985). The formation subdivision into members, called Member 1–4, was proposed by Wang et al. (1998), who referred to the Tianjiayuanzi type section and characterized these in general lithological terms. However, the succession of the nominal type section has neither been presented (only the ‘representative section’ in Miaohe), nor have the member boundaries indicated in the measured succession levels and defined. The members of the Doushantuo Formation have been followed, but respectively referred to as Member 1–4 (Zhu et al. 2003; Lu et al. 2012), member 1–4 (Zhou & Xiao 2007), member I–IV (Zhou et al. 2007; McFadden et al. 2008) and Member I–IV (Xiao et al. 2010, 2012; Liu et al. 2013, 2014a, b; Zhou et al. 2017a), or substituted by five numbered units 1–5 with the rank of member (Xiao et al. 2014a; Zhou et al. 2017b). The recognition of members in the Doushantuo Formation remains to be formalized and here the members are considered informal (Fig. 2). Lu et al. (2012) studied the Tianjiayuanzi section and presented as a 170‐m‐thick succession with distinct members, but only the lower and upper portions could be measured because the

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Fig. 2. General lithologic succession and stratigraphic subdivision of the Ediacaran strata in the Yangtze Platform, South China. The Ediacaran chronostratigraphic subdivision and the ages of the Doushantuo Formation are according to Condon et al. (2005) and Ogg et al. (2016). Lithostratigraphy and sedimentology of the Doushantuo Formation is compiled from various publications referenced to in the text and by own studies (Liu et al. 2013, 2014a, b), but the recognition of stratigraphic hiati that are marked by vertical lines in red and conventional symbol is largely our interpretation. The chronostratigraphic column is drawn proportionally to the time frame and duration of the Ediacaran intervals corresponding to particular rock successions (lithostratigraphic members) but not to their thicknesses. The hiati at the levels of unconformities are of unknown duration.

strata are mainly covered in the middle part of the section. As significantly recognized in this section, the Doushantuo Formation unconformably overlies the Nantuo diamictite, and basal and topmost layers of the cap carbonate are strongly disrupted by stromatactis‐like cavities, siliceous crusts and sheet cracks (Lu et al. 2012; Fig. 2). These features confirm the inferred unconformities at the base of the Doushantuo Formation and at sequence boundary 1 (SB1) at the top of the cap carbonate (Wang et al. 1998; Zhu et al. 2007b, 2013; Lu et al. 2012). The unconformity at the base of the Ediacaran System involves a hiatus with a duration of ca. 1 Ma (Zhang et al. 2008; Lu et al. 2012; see also under the Jiuqunao section) and is any good example of the newly introduced concept of xenoconformity at this stratigraphic level posited by Halverson (2017). Two additional unconformities in the Tianjiayuanzi section mark sequence boundary SB2 in the middle of Member 2, and SB3 at the uppermost Member 3 (Lu et al. 2012). The lower unconformity is covered but is inferred to occur at 40 m level, whereas the upper unconformity is well exposed and recognized as the erosional surface with irregular karstic infilling of ooids at the top of Member 3. Located near the Tianjiayuanzi section and parallel to it extending across

the valley is the Chenjiayuanzi succession studied here (see below).

The Doushantuo Formation lithostratigraphy The Doushantuo Formation in the Yangtze Gorges is underlain by the Cryogenian Nantuo Formation diamictite and overlain by the upper Ediacaran Dengying Formation dolostone. It has well‐defined lower and upper boundaries, namely at the base of the cap carbonate and the top of organically rich black shale at the uppermost part of the formation and at the contact with the overlying massive crystallized dolostone of the Dengying Formation (Jiang et al. 2006, 2011; Zhu et al. 2007b, 2013; Zhou et al. 2007; Lu et al. 2012; Fig. 2). The Doushantuo Formation subdivision into four informal members identified by lithologic characteristics has been recognized in numerous studied sections (Wang et al. 1998; Zhu et al. 2003, 2013; Zhou & Xiao 2007; Zhou et al. 2007, 2017a; McFadden et al. 2008; Jiang et al. 2011; Lu et al. 2012; Liu et al. 2013, 2014a, b). The lower and upper boundaries of individual members are placed at the levels of abrupt lithologic change coinciding with changes in the lithofacies (with some

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Ediacaran microfossils from the Doushantuo Formation

exceptions) in various localities. Alternatively, the Miaohe Member in the uppermost Doushantuo Formation of the Miaohe section (Xiao et al. 2002; also remaining as an informal unit) is used in stratigraphic terminology as the approximate equivalent to member IV (Condon et al. 2005; Xiao et al. 2010; Zhu et al. 2013; Zhou et al. 2017a; but see also An et al. 2015 for a different interpretation). Some researchers do not use the member subdivision of the Doushantuo Formation and follow metre‐scale logging instead (Yin et al. 2007b; Zhu et al. 2007b, 2013; McFadden et al. 2009; Xiao et al. 2012; Lu et al. 2013). Local unit terms such as ‘lower and upper dolomite’, ‘Lower Carbonate’, ‘Lower and Upper Sequence’ and ‘lower and upper phosphorite’ are used, depending on the regional lithostratigraphy (Condon et al. 2005; Zhou et al. 2017a). This is because the Doushantuo Formation differs substantially in its facies development and lateral change between the Yangtze Gorges and the southern area of the Yangtze Platform (Zhu et al. 2007b; Jiang et al. 2011; Zhou et al. 2017a), and the lithostratigraphic units are not yet confidently correlated. We will follow referencing to the four lithostratigraphic units that have been distinguished as members I–IV, accepting the time equivalence between the Miaohe member and member IV (Fig. 2). The four informal members (I–IV) of the Doushantuo Formation in the type area that are studied here are in stratigraphical order: member I is a 5‐m‐thick cap dolostone that overlies the glaciogenic deposits of the Nantuo Formation; member II is a 60‐ to 140‐m‐thick black shale intercalated with medium‐bedded dolostone and muddy dolostone with abundant chert nodules and occasionally limestone; member III is a 40‐ to 60‐m‐thick medium‐ bedded dolostone with chert bands or lenses and banded dolostone (limestone interbedded with dolostone); member IV is a 10‐ to 20‐m‐thick black shale with large dolomitic concretions (Jiang et al. 2006; Zhou et al. 2007; Xiao et al. 2010; Liu et al. 2014b; Fig. 2). The thickness of members varies between the localities in the Yangtze Gorges area, and more substantially in the equivalent units in the southern part of the Yangtze Platform (Zhu et al. 2013). The entire formation can be seen to be wedging out or waning across the platform areas due to the configuration and topography of the sedimentary basin but it also comprises sedimentary gaps. The Doushantuo Formation members are well recognized in Yangtze Gorges area but not in other areas of the Yangtze Platform (Xiao et al. 2012). The members I and II can be mapped around the Huangling Anticline (Fig. 1B). However, member IV shows larger variation in the thickness and it is

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absent in the eastern part of the Huangling Anticline area, whereas in the western area the stratigraphic equivalent is referred to the Miaohe Member (Xiao et al. 2010; Liu et al. 2013, 2014b; Zhou et al. 2017a). This member is 20 m thick and consists of organic‐ rich shale. It is the uppermost member of the Doushantuo Formation in the Miaohe section (Yangtze Gorges) and deposited in a subtidal restricted basin during the marine transgression on a shallow platform (Wang et al. 1998; Xiao et al. 2002). It is distinguished within the succession by the uniquely preserved macroscopic carbonaceous compression fossils of so‐called Miaohe biota, which represent predominantly multicellular, red and green algae and some of uncertain origin organisms (Steiner 1994; Xiao et al. 2002). This type of biota has also been recognized in some other sections (Xiao et al. 2010; Ye et al. 2017; Zhou et al. 2017a). The Doushantuo succession interval assigned to member III consists of dolostone, limestone and minor shale, or so‐called ribbon rock (limestone interbedded with dolostone; Xiao et al. 2010), and these lithologies are laterally exchanged and assumed to be contemporaneous stratigraphically (Jiang et al. 2011; Zhu et al. 2013; Zhou et al. 2017a). The lithostratigraphy of the Doushantuo Formation merits that its successions be revised and described using a common standard of lithologic classification; the stratotype section should be designated, the subdivision into members formally defined, and the reference sections consistently measured from zero level to make correlation and comparisons feasible.

Depositional environments The general reconstruction of the lithofacies distribution and depositional environments show the Yangtze Platform as a complex palaeogeographic system (Jiang et al. 2011; Zhu et al. 2013; and references there) that evolved during the extensional tectonic and post‐rifting sag phase of subsidence in the Cryogenian–Ediacaran periods and subsequently became a passive margin (Li et al. 2003; Pisarevsky et al. 2003; Wang & Li 2003; Vernhet et al. 2007). During the early–middle Ediacaran, which is the Doushantuo Formation depositional time, the Yangtze Platform formed a rimmed carbonate platform with a tidally influenced shallow shelf (tidal flats) and a restricted basin (shelf lagoon), which was delimited by the barrier shoals from the slope and the open ocean (Vernhet et al. 2007; Zhu et al. 2007b, 2013; Vernhet & Reijmer 2010; Jiang et al. 2011). A variety of carbonate and fine‐grained siliciclastic facies associations developed across these depositional environments and laterally changed, not only between the

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shelf‐to‐slope and basin zones, but also typically along the shelf with pinching‐out and deepening lithofacies, including areas of non‐deposition and erosion. The Yangtze Gorges occupied the peritidal– subtidal shale‐carbonate marginal zones (Jiang et al. 2007, 2011; Zhu et al. 2007b; Bristow et al. 2009; Xiao et al. 2012) that were ecologically favourable for life development and preserved in situ an abundant fossil record (Yin & Li 1978; Zhang 1984; Yin 1985, 1987; Yin & Liu 1988; Zhang et al. 1998a, b; Xiao 2004; Yin et al. 2007b, 2011b; Zhou et al. 2007; Liu et al. 2009a, b, 2013, 2014b; McFadden et al. 2009). Fossils include uni‐ and multicellular algae (red, green and brown), metazoans of the Ediacara‐type, sponge and putative metazoan embryos (Yuan et al. 2002). The detailed sedimentological and sequence stratigraphy interpretations of the Doushantuo Formation are not yet available or unified in a regional scale and may differ between areas of the Yangtze Platform that have been studied, but two major unconformities and sequence boundaries have been recognized. They are evident in several sections, such as the Wuhe‐Gaojiaxi, Tianjiayuanzi and Miaohe sections (Yangtze Gorges area), the Yangjiaping section (south of the Yangtze Gorges) and the Weng'an section (southern part of the platform) (Zhu et al. 2007b, 2013; Jiang et al. 2011; Lu et al. 2012; Xiao et al. 2014a, b). The lower unconformity is also recorded in the Yangtze Gorges area in the northern Xiaofenghe, Jiulongwan and Wanjiagou sections, whereas the upper unconformity or its equivalent, recognized as the ‘regional discontinuity’ marked by the abrupt facies change, is recorded in the Jiulongwan and Jijiawan (= Jiuqunao) sections (Zhu et al. 2007b; Jiang et al. 2011; Lu et al. 2012). These two regional unconformities are marked by the eroded surfaces and associated with the presence of karst breccia within the middle and upper parts of the Doushantuo Formation in the inner shelf zone of the platform (Yangjiaping section) and in the outer shelf (Weng'an section) (Xiao & Knoll 1999; Zhu et al. 2007b; Jiang et al. 2011; Lu et al. 2012; Xiao et al. 2014a; Fig. 3). Three depositional sequences distinguished within the Doushantuo Formation (S1, S2, S3, in ascending order) are marked by sequence boundaries at erosional unconformities (SB2, SB3) and sharp lithologic contact (SB1 at the base of cap carbonate) (Zhu et al. 2007b). The base of the Doushantuo Formation and cap carbonate (SB1) has also been interpreted as the level of uncertain unconformity (Wang et al. 1998; Jiang et al. 2011; Lu et al. 2012). The depositional sequences record two successive transgressions and high stands tracts of shallowing upward cycles over the platform and the beginning of the third

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cycle (Kennedy 1996; Wang & Li 2003; Condon et al. 2005; Vernhet et al. 2007; Zhu et al. 2007b, 2013; McFadden et al. 2008, 2009; Jiang et al. 2011). The two erosional unconformities within the formation are laterally represented in some areas by the time‐ equivalent abrupt facies change that coincides with flooding surfaces (summary in Jiang et al. 2011; Zhu et al. 2013). Alternatively to the depositional sequences, three transgressive‐regressive cycles were identified in the Doushantuo Formation and the lower Dengying Formation. While defined by ‘discontinuities’ they are not bounded by subaerial exposure surfaces to be recognized as typical sequences (McFadden et al. 2008, 2009). The three sequences embrace the Doushantuo succession intervals as follows: (S1) including the member I and the lower part of member II, (S2) upper member II and most of member III, and (S3) topmost member III, member IV and the lower Dengying Formation (Jiang et al. 2011; Lu et al. 2012; Zhu et al. 2013). The stratigraphic position of unconformities interpolated in reference to members in the sections studied by Zhu et al. (2013) remains uncertain because these authors have not distinguished members, but have used metre‐scale logging, and the zero level in the sections measured differs in various publications. Our understanding is that in addition to the two recognized unconformities (or three, if one includes the base of cap carbonate as an unconformity), several paraconformities exist at different levels within the Doushantuo Formation, namely at the levels of abrupt facies change in the sections studied (see Figs 2, 3). The paraconformities and involved sedimentological and stratigraphic gaps are evident in the sections where member IV is missing (see below) and at some other levels. Their existence is consistent with the relatively thin sediment succession observed in the Doushantuo Formation (max. 220 m thick or 105 m in the isotopically dated Jiuqunao = Jijiawan section) that spans a long depositional time of ca. 84 Ma and 90% of the Ediacaran Period (Condon et al. 2005; Ogg et al. 2016). This reduced thickness is not only owing to assumed and the extremely low rate of deposition (Xiao et al. 2012), which was calculated based on the erroneous assumption of successions being continuous (Zhu et al. 2007b) or condensed (Xiao et al. 2012; Zhu et al. 2013). However, the existence of possible multiple hiati have not been excluded (Xiao et al. 2012).

Age of the Doushantuo Formation The absolute age of the Doushantuo Formation has been established by zircon U‐Pb dating in the ash

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 3. Stratigraphic succession of the correlative but fragmentarily preserved Ediacaran strata in the Weng'an section, Guizhou Province, and the Zhangcunping section, north of the Yangtze Gorges, of the Yangtze Platform showing unconformities and stratigraphic hiati of various duration. The red asterisks mark the occurrence of the Weng'an biota in the Weng'an section and some microfossils in common with the Zhangcunping section. The ages from both successions and microfossil occurrences are according to Liu et al. (2009b), Xiao et al. (2014a) and Zhou et al. (2017b). The chronostratigraphic column is drawn proportionally to the Ediacaran time frame but not to the succession thickness that is only a few tens of metres. Graphic lithologic symbols as in Figure 2.

layer of the Wuhe‐Gaojiaxi section 2.3 m above the base of the formation at 635.2 ± 0.6 Ma, and in the Jijiawan section in two ash layers: one 5 m above the cap carbonate at 632.5 ± 0.5 Ma, and the other in the topmost of the Miaohe Member (= member IV) at 551.1 ± 0.7 Ma (Condon et al. 2005). The same section studied at Jijiawan but named Jiuqunao (Zhu et al. 2007b), provided the U‐Pb zircon age of 621.5 ± 7 Ma for the ash bed 2.5 m above the cap carbonate within the lowermost Doushantuo Formation, and of 555.2 ± 6.1 Ma for the ash bed 1.5 m below the boundary with the overlying Dengying Formation (Zhang et al. 2005). These isotopic ages are consistent within the measurements margin of error, and the time interval of 635.2–551.1 Ma is commonly accepted as the age of the Doushantuo Formation in the Jiuqunao section (Figs 1B, 5), where the total Doushantuo Formation thickness is 105 m and spans a time interval of 84 Ma. The Doushantuo Formation is generally referred to the lower–middle Ediacaran (Narbonne et al. 2012; Xiao

et al. 2016), and the preceding Nantuo Formation is contemporaneous with the Marinoan glaciation at 637–635 Ma (Zhou et al. 2004b; Condon et al. 2005; Calver et al. 2013; Ogg et al. 2016).

Materials and methods Organic‐walled microfossils preserved by early diagenetic permineralization in chert nodules within dolostone and shale in the Doushantuo Formation were studied in petrographic thin sections under a Nikon 80i and Zeiss Imager A2 transmitted light microscopes and digitally photographed by attached Nikon DS‐Ri1 and AxioCam MRc5 cameras, respectively. The chert samples were collected from eleven sections (Fig. 1) and more than 185 stratigraphic layers containing chert nodules within dolostone across members II and III of the formation. The studied geological successions were logged and their measurements may differ in detail from those previously

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published in certain sections. The lithostratigraphic subdivision into members I–IV of the Doushantuo Formation follows the scheme by Liu et al. (2014b). The chert nodules were cut parallel and perpendicular to the bedding plane of the host strata and polished into ca. 50‐μm‐thin sections that were both covered and non‐covered by glass slips. Ten thin sections, or in some cases more, from each sample were examined for microfossils; 159 samples appeared fossiliferous (Figs 4–14). The microfossil abundance in a single sample (rendered into 10 thin sections) is sparse, varying from a few to ten specimens and occasionally hundred. The above microfossils are in a state of preservation that varies from excellent to poor, but are mostly good. They show the taphonomic phases resulting from the processes of syn‐sedimentary accumulation, early biodegradation and subsequent impregnation by the mineral solutions and the precipitation of diagenetic minerals. The specimens were observed in their vesicle sections and at limited optical focus. It was not possible to see the entire vesicle surface or the distribution pattern of morphologic elements on the surface (processes, extensions, microsculpture). On the other hand, the sections of the vesicle wall

FOSSILS AND STRATA

and processes clearly show the wall thickness, wall layers and outer wall lamination, whether processes are hollow or solid, and the connection between the processes and the vesicle cavity. The specimens observed were slightly collapsed. Minor compression folds were occasionally observed even in thin sections but predominantly the specimens seemed to be three‐dimensionally preserved due to infilling by silica. The effect of silica impregnation is an inflation of the vesicle, processes, and particularly their bases, which may appear wider and stiffer. This is often a taphonomic, not a morphological or diagnostic feature. The taphonomic alteration of the shape of processes (bases ‘inflated’) and the vesicle size possibly increased in permineralized specimens (by silica as well as phosphate) in contrast to the specimens that were organically preserved in shale (vesicles compressed but also three‐dimensionally preserved, bases ‘deflated’) are not always recognized. The taphonomy of microfossils continues to be discussed as to its effect on species recognition (Grey 2005; Moczydłowska 2005; Grey & Willman 2009; Xiao et al. 2010). Many taphonomic variants with slightly differing process shapes and dimensions (depending on the mode of preservation) may represent

Fig. 4. Lithostratigraphic succession of the Doushantuo Formation in the Baiguoyuan section with microfossil occurrence and carbon isotope values. Isotope data from Zhu et al. (2013b). For legend and abbreviations see Figures 7 and 10, for this and all figures 4–14. The succession in this and following figures 5–14 are all attributed to the Doushantuo Formation.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

9

Fig. 5. Lithostratigraphic succession in the Jiuqunao (= Jijiawan) section with microfossil occurrence. Isotopic ages from Condon et al. (2005).

the same species (phenotypes), and thus, some Ediacaran form‐species are subjective and superfluous making the total number of species lower.

Repository The microfossil collection is housed at the Institute of Geology, Chinese Academy of Geological Sciences, Beijing, and is assigned to the catalogue number with the pre‐fix IGCAGS.

Studied geological successions The studied successions of the Doushantuo Formation are exposed in the flanks of the Huangling Anticline, which occupies the northern part of the Yangtze Platform (Fig. 1A, B). Some among those successions have been previously investigated for organic‐walled microfossils and proven to contain assemblages that are biostratigraphically significant but known predominantly in the middle part of the formation (member III; Zhang et al. 1998b; Xiao 2004; Yin et al. 2007b, 2008, 2011b; Yin et al. 2007a, 2009a, b; Zhou et al. 2007;

Xie et al. 2008; McFadden et al. 2009; 2011a; Liu et al. 2012b, 2013, 2014a, b; Ouyang et al. 2015; Ye et al. 2015). This research is focused on the basal part of the formation and member II with some additional work on member III. The first reports on microfossils are from the Liuhuiwan and Dishuiyan sections. Microfossils are obtained from chert nodules in dolostone and are listed in Table 1, and in sections’ lithostratigraphic logs (Figs 4–14). The Huangling Anticline comprises the Archaean– Palaeoproterozoic basement rocks and granite of ca. 820 Ma in the axis of the anticline and is surrounded by Tonian–Triassic sediments which include a narrow belt of the Cryogenian–Ediacaran strata (Fig. 1B) studied here. The Cryogenian–Ediacaran succession consists of the glaciomarine Nantuo Formation and the overlying Doushantuo and Dengying formations, respectively (Zhu et al. 2003, 2007b, 2013; Zhou et al. 2007; Liu et al. 2013; Figs 2, 3). The Huangling Anticline is cut by a system of major regional faults trending in general NE–SW directions and the Cryogenian–Ediacaran successions in its marginal zone are variable preserved in their stratigraphical extent, incomplete and partially exposed.

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Fig. 6. Lithostratigraphic succession in the Jiulongwan section with microfossil occurrence. The erosional surface at the level of 125 m and paraconformity is newly observed.

The most complete successions of the Doushantuo Formation are exposed in the southern flank of the anticline that is delimited by the fault occupied by the Yangtze River. These successions comprise all four members of the formation, overlie the Nantuo Formation and are succeeded by the Dengying Formation, both formations servings as the stratigraphic reference levels. They are studied in the Jiuqunao

FOSSILS AND STRATA

(previously called Jijiawan), Jiulongwan and Chenjiayuanzi sections (Fig. 1B). The remaining sections in the eastern and northern flanks of the anticline expose partially the Doushantuo Formation in its intervals embracing the members I–II–III or II–III‐ IV, and of variable thicknesses. As aforementioned, in a close vicinity to the Chenjiayuanzi section, the Tianjiayuanzi type section of the Doushantuo Formation is located, where the members were originally described (Wang et al. 1998) although not formally recognized. Among numerous known sections of the Doushantuo Formation, the Jiuqunao, Jiulongwan and Xiaofenghe are considered to be the ‘reference sections’ in the type area. In these sections, the isotopic ages of the formation have been obtained (Jiuqunao; Condon et al. 2005; Yin et al. 2005; Zhang et al. 2005), the lithostratigraphic members adopted (Zhou et al. 2007) and chemostratigraphic signatures studied (Jiang et al. 2007; Zhu et al. 2007b, 2013; Xiao et al. 2012; Zhou et al. 2017a). The Xiaofenghe section is a composite geological succession that is exposed in two sections, namely the northern with the lower portion and the southern with the upper portion of the Doushantuo Formation yet without exposed contact with the Dengying Formation (Xiao et al. 2012; Zhu et al. 2013; herein). The Xiaofenghe section was earlier shown as a single succession beneath the Dengying Formation (Yin et al. 2007b, 2008; Zhu et al. 2007b; McFadden et al. 2009; Yin et al. 2011a; Liu et al. 2013, 2014b). The total composite thickness of the Doushantuo Formation in the northern and southern sections, which is at the maximum observed in the Yangtze Gorges area, is ca. 220 m (Zhu et al. 2007b) or 190 m measured herein. Since the discovery of microfossils in the Doushantuo Formation some 40 years ago (Yin & Li 1978; Zhang 1981a, b, 1982, 1985, 1986; Yin 1985, 1987), the representative sections have been continuously studied for microfossils and in a pursuit of their biostratigraphic application (Yin & Liu 1988; Yuan et al. 1993, 2002; Xiao et al. 1998, 1999, 2000, 2007, 2014a; Yuan & Hofmann 1998; Zhang et al. 1998; Xiao & Knoll 1999, 2000; Zhou et al. 2001, 2007, 2017a; Xiao 2004; Yin et al. 2007a, b, 2008, 2009a, b, 2011a, b; Liu et al. 2008, 2009b, 2010, 2012a, b, 2013, 2014a, b; McFadden et al. 2009; Ouyang et al. 2015; Ye et al. 2015). Our new record extends the known occurrence and stratigraphic ranges of microfossil species in the lower Doushantuo Formation and enriches the diversity of the middle part of the formation. The here measured sections and their lithologic descriptions and thicknesses may differ to some extent from the stratigraphic logs reported by

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

11

Fig. 7. Lithostratigraphic succession in the Chenjiayuanzi section with microfossil occurrence and carbon isotope values. Isotope data from Liu et al. (2014a). The paraconformity or erosional surface at the level of 152 m is newly recognized.

previous authors, as they also differ between discrete publications, owing to the state of current exposure and lithological classification standards used. We briefly describe the studied sections and do not intend to revise them or interpret sedimentologically. However, we pay attention to recognizing sedimentological unconformities, paraconformities and time hiati to evaluate the stratigraphic completeness of the successions for the purpose of potential biostratigraphic subdivision of the Doushantuo Formation. Because the subdivision of the Doushantuo Formation into members has yet to be defined according to the international stratigraphic rules, we further refer to members I–IV as to informal lithostratigraphic units. This will also refer to the Miaohe ‘Member’ (Zhu et al. 2013; Zhou et al. 2017a) which still remains as informal member.

The Baiguoyuan section The Baiguoyuan section is located at the northwestern flank of the Huangling Anticline (Figs 1B, 4), and the outcrop of the Doushantuo Formation is

along the village hillside. The 128‐m‐thick succession starts at a road‐cut exposing a 4‐m‐thick phosphorite bed, which is the major phosphorite horizon and correlative level within member II in the area. The cap carbonate of member I and the lowermost part of member II are not observed. The succession is overlain by the lower Dengying Formation that is a good stratigraphic reference level. In the Baiguoyuan section, the Doushantuo Formation consists of the partially exposed member II (60 m thick) and the overlying member III (55 m thick) and member IV (13 m thick). The boundaries between the members II, III and IV, as well as with the Dengying Formation are at abrupt lithological changes between black shale (members II and IV) and dolostone (member III and the basal Dengying Formation). The lower part of member II in this section consists of a 4‐m‐thick phosphorite bed that is overlain by 6 m of light grey and thick‐bedded dolostone, and 10 m of grey medium‐bedded dolostone with minor interbeds of black shale (with a single bed thickness ~10 cm). This interval is succeeded by 40 m of black shale with

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Fig. 8. Lithostratigraphic succession in the Nantuocun section with microfossil occurrence.

minor grey thin‐ to medium‐bedded muddy dolostone (upper member II), which is partly covered. The overlying 55 m of grey dolostone of member III form a steep cliff in the area. The lower part of the member is composed of 16 m of grey medium‐ bedded and laminated dolostone with minor shale interbeds. Thin‐bedded or irregular layers of banded chert (a single layer less than 5 cm thick) occur frequently in this interval. The overlying 20 m of grey medium‐bedded, laminated dolostone is associated with abundant cherty nodules and is overlain by 19 m of grey medium‐ to thick‐bedded dolostone. The member IV consists of a 13‐m‐thick black shale with thin dolostone interbeds and is overlain

FOSSILS AND STRATA

by grey, medium‐bedded dolostone of the lower Dengying Formation. This interval has been alternatively referred to the Miaohe member by Zhu et al. (2013). Zhu et al. (2013) indicated two unconformities or sequence boundaries in the Baiguoyuan section, both with sharp contacts between dolostone and shale intervals. The lower unconformity is at –75 m in their stratigraphic log and situated between the dolostone and overlying shale, but it has not been clearly recognized here. This level should be within the succession of black shale with muddy dolostone of member II but it was partly covered. In our measured section, using the same zero level at the base of member IV (= Miaohe member), the lower unconformity should be at 95 m (Fig. 4). The upper unconformity was indicated to be at the base of the Miaohe member (Zhu et al. 2013), and at the sharp contact between dolostone of member III and black shale of member IV (Fig. 4). This unconformity has been interpreted as a flooding surface (Jiang et al. 2007) and a major sequence boundary and erosional surface between sequences 2 and 3 in the Doushantuo Formation (Zhu et al. 2013). Some discrepancies exist between the attribution of the succession intervals to the members and their thicknesses in the Baiguoyuan section. In difference to the present log, the member IV or the Miaohe member is cited as a 20‐m‐thick black shale (Zhu et al. 2013), whereas member III as only a 30‐m‐thick dolostone with chert nodules (Zhou et al. 2017a), or members are not recognized with the exception of the Miaohe member (Zhu et al. 2013). The litho‐ and chemostratigraphic correlation of the succession in a regional scale (Zhu et al. 2013; Zhou et al. 2017a) may be difficult to follow if not bound to consistent intervals of the sedimentary succession. The carbon isotope studies in this section have shown fluctuations throughout the Doushantuo Formation (Zhu et al. 2013; Zhou et al. 2017a). The carbon isotope values from the carbonates in member II of the section are positive with δ13C values from +5‰ to +6‰, whereas those in the upper part of the section show two major negative excursions. The lower excursion from the lower part of member III shifts from +6‰ to −5‰ within an interval of about 4 m and is referred to the BAINCE excursion (that is BAIguoyuan Negative Carbon isotope Excursion; Zhu et al. 2013). The upper one is recorded in the uppermost part of member III and into member IV with δ13C values shifting from +5‰ to −7.5‰ (Zhu et al. 2013, fig. 7; Fig. 4). This upper excursion has been recognized also in other sections of the Doushantuo Formation and is named the EN3 (Ediacaran Negative excursion 3; Zhou & Xiao 2007) or

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

13

Fig. 9. Lithostratigraphic succession in the Wangfenggang section with microfossil occurrence.

DOUNCE excursion (DOUshantuo Negative Carbon isotope Excursion; Zhu et al. 2007a, 2013). It has been correlated with the global Shuram‐Wonoka excursion (Jiang et al. 2007, 2011; Zhou & Xiao 2007; Zhu et al. 2007a; Zhu et al. 2013). The observed variations in carbonate δ13C values have been argued to reflect the secular trends in ocean chemistry (Fike et al. 2006; Zhou & Xiao 2007; Zhu et al. 2013; Zhou et al. 2017a); however, the two negative excursions in the Baiguoyuan succession coincide with abrupt facies change and unconformities or paraconformities (Fig. 4). The primary origin and global synchroneity of the negative carbon isotope anomalies remain uncertain and the model for rapid oxygenation and carbon cycling in the Ediacaran

Period, including the best studied Shuram‐Wonoka anomaly, is debated (Derry 2010; Grotzinger et al. 2011; Lu et al. 2013; but see Minguez & Kodama 2017). Liu et al. (2013) have reported microfossils from this section and identified a few acanthomorphic species from the middle part of member III, including Cavaspina acuminata, Knollisphaeridium maximum, K. triangulum and Tanarium conoideum. T. conoideum has been subsequently considered in part synonymous with Hocosphaeridium scaberfacium (Liu et al. 2014b) and the latter species is listed in the present Figure 4 along with T. conoideum. One of the present authors (MM) expresses reservation to the taxonomic recognition of Hocosphaeridium (see

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FOSSILS AND STRATA

Fig. 10. Lithostratigraphic succession in the Niuping section with microfossil occurrence and carbon isotope values. Isotope data from Liu et al. (2014b)

chapter descriptions) and the presence of H. scaberfacium in the Baiguoyuan and other sections. She considers that the latter species represents Tanarium conoideum (see Liu et al. 2013, fig. 11A). In the present study, 11 chert horizons from the middle part of member III were examined and seven yielded acanthomorphic species although rare in abundance, including 10 genera and 16 species (Fig. 4). In the new assemblage recovered in the section (Fig. 4), the significant species are Ancorosphaeridium magnum, Appendisphaera grandis, Hocosphaeridium scaberfacium, Knollisphaeridium maximum, Schizofusa zangwenlongii, Tanarium conoideum, T. paucispinosum and T. pilosiusculum because they occur on other Ediacaran palaeocontinents providing the basis for interregional biostratigraphic correlation. In Australia, the species H. scaberfacium is attributed to Tanarium conoideum (Grey 2005).

The Jiuqunao section (= Jijiawan) The Jiuqunao section is located at the southwestern flank of the Huangling Anticline, about 30 km southwest of Zigui town (Fig. 1B), and it was previously

called the Jijiawan section (Condon et al. 2005; Zhu et al. 2007b). The section is exposed along S334 Road from Guojiaba to Zigui on the southern side of the Yangtze River. The total thickness of the Doushantuo Formation is 105 m and its basal 4‐m‐thick cap dolostone of member I directly overlies the Nantuo diamictite (Fig. 5). It is succeeded by a 46‐m‐thick interval of black shale with interbeds of black medium‐bedded muddy dolostone with chert nodules of member II. Above this interval, the section is poorly exposed for about 12 m but presumably the strata belong to the same member. The overlying succession is 30 m of grey, medium‐ to thick‐bedded dolostone of member III, including 6 m of medium‐ bedded muddy dolostone with irregular or banded chert layers (a single layer less than 5 cm thick) at the base. Member IV consists of a 12‐m‐thick black shale and cherty black shale and then 1 m of grey, medium‐bedded muddy dolostone. The Doushantuo Formation is overlain with a sharp lithologic contact by light grey, massive dolostone of the Dengying Formation. The stratigraphic column of the Jiuqunao section presented by Yin et al. (2011a) differs significantly in the lithologic identification from the succession

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

15

Fig. 11. Lithostratigraphic succession of the Doushantuo Formation in the northern Xiaofenghe section with microfossil occurrence and carbon isotope values. Isotope data from Xiao et al. (2012b)

shown here in respect to the interval attributed to member II (Fig. 5). Although not referenced to a measured log but only to informal members, the interval of member II comprised predominantly dolostone with interbeds of shale (Yin et al. 2011a) in contrast to the mostly shale‐containing interval observed herein (Fig. 5). All four members of the Doushantuo Formation in this section are recognized by characteristic lithologies and their boundaries occur at levels of abrupt lithological change. These boundaries occur at the levels of unconformities (between members III and IV) and likely paraconformities (member I–II, II–III) with concealed depositional breaks. The individual members are highly reduced in thickness in comparison with other sections. The lower boundary

of the Doushantuo Formation is recognized by the transgression surface at the base of the cap carbonate overlying the Nantuo Formation diamictite (Jiang et al. 2003, 2006, 2011), and this surface is here argued to occur also at the level of a paraconformity. The abrupt change between the depositional regime of diamictites, which were formed under cold climatic conditions, and the precipitation of cap carbonate, which occurred in warm climatic conditions, could not have happened instantaneously and indicates the paraconformity involving time hiatus. The hiatus corresponds to a time interval of deglaciation (during which such climate change took place) and may be relatively short. It is estimated to 0.9–1.5 Ma using the isotopic ages of the basal layer of the Nantuo Formation at 636.3 ± 4.9 Ma and the cap

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FOSSILS AND STRATA

Fig. 12. Lithostratigraphic succession in the southern Xiaofenghe section with microfossil occurrence.

carbonate at 635.2 ± 0.6 Ma (Condon et al. 2005; Zhang et al. 2008). The sharp lithologic contact between the Nantuo diamictite and the basal Doushantuo cap carbonate is marked by the persistent occurrence of a thin claystone layer between these formations across the Yangtze Platform (Zhang et al. 2008). This boundary claystone layer consists of kaolinite, which is a clay mineral diagnostic of subaerial weathering, and indicates a non‐deposition and a time lag between the Nantuo and the Doushantuo formations (Zhang et al. 2008). The ‘time lag’ is the hiatus of ca. 1 Ma duration at the paraconformity separating the two formations at the regional scale across the Yangtze Platform (Figs 2, 3). The succession of diamictite and cap carbonate may only apparently appear to be sedimentologically continuous in certain sections but it comprises a sedimentological break and paraconformity. In the Jiuqunao succession, Zhu et al. (2007b) identified an unconformity at the level of a sharp

lithologic contact between dolostone and black shale and shown by an irregular surface that represents a sequence boundary and flooding surface that is here identified at the boundary between members III and IV (Fig. 5). The reduced thickness of the Doushantuo Formation to ca. 105 m in this section (Fig. 5) that spans ca. 84 Ma time interval (Condon et al. 2005) could not be accepted as only the result of extremely low rates of sedimentation and condensation of the succession as it was commonly perceived for the Doushantuo Formation. The succession is a normal lithologically shale‐carbonate succession, without hard grounds or any signs of stratigraphic condensation. The presence of sharp contacts between distinct lithologic intervals (= lithostratigraphic members) may coincide with paraconformities, non‐deposition and stratigraphic gaps succeeded by flooding surfaces (boundaries between members I‐II and III‐IV), or regression surface (members II‐III). The

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

17

Fig. 13. Lithostratigraphic succession in the Dishuiyan section with microfossil occurrence.

Fig. 14. Lithostratigraphic succession in the Liuhuiwan section with microfossil occurrence.

unconformity or sequence boundary inferred by Zhu et al. (2007b) at the boundary between members III and IV would explain the reduced thickness of members III and IV that is observed in comparison with other sections. The paraconformity, suggested here, at the boundary between members II and III would explain the reduced thickness of member II, which is almost twice thicker in the Jiulongwan and

Chenjiayuanzi sections. This difference could not only be due to the sedimentological pinching‐out or topography of the basin or rate of sedimentation. Zircon U‐Pb dating of the two ash layers at the bottom and the top in this section yielded ages of 632.5 ± 0.5 Ma and 551.1 ± 0.7 Ma, and together with the age of 635.2 ± 0.5 Ma from the Wuhe-Gaojiaxi section, the Doushantuo Formation is bracketed at 635–551 Ma (Condon et al. 2005). Microfossils are recorded for the first time in this section from 7 chert horizons in the member II. They consist of 14 genera and 18 species (Fig. 5). Among them, Tianzhushania spinosa and Yinitianzhushania sp. were diagnostic of the earliest assemblage and biozone in the Yangtze Gorges area that was restricted to the lower part of member II (Liu et al. 2013, 2014a, b). In a newly proposed zone (Fig. 16), T. spinosa is one of the nominal species. Other species, such as Mengeosphaera gracilis, Schizofusa zangwenlongii and Tanarium tuberosum that occur in member III in other sections in the Yangtze Gorges area (Liu et al. 2013, 2014a, b), are recorded here for the first time in member II, extending their stratigraphic ranges. Biostratigraphically significant species that are known worldwide and that occur here include Appendisphaera grandis, Tanarium tuberosum and Multifronsphaeridium pelorium. Six new species are described in this

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FOSSILS AND STRATA

Table 1. Acritarch species from the Ediacaran Doushantuo Formation in the Yangtze Gorges area, South China. Taxon 1. Alicesphaeridium medusoideum Zang in Zang and Walter, 1992, emend. Grey, 2005 2. Ancorosphaeridium magnum Sergeev et al., 2011, emend. Moczydłowska, 2015 3. Appendisphaera anguina Grey, 2005 4. Appendisphaera brevispina Liu et al., 2014 5. Appendisphaera clava Liu et al., 2014 6. Appendisphaera clustera n. sp. 7. Appendisphaera grandis Moczydłowska et al., 1993, emend. Moczydłowska, 2005 8. Appendisphaera hemisphaerica Liu et al., 2014 9. Appendisphaera lemniscata n. sp. 10. Appendisphaera longispina Liu et al., 2014 11. Appendisphaera longitubulare (Liu et al., 2014) n. comb. 12. Appendisphaera setosa Liu et al., 2014 13. Appendisphaera tabifica Moczydłowska et al., 1993, emended 14. Appendisphaera tenuis Moczydłowska et al., 1993, emend. Moczydłowska, 2005 15. Asseserium diversum Nagovitsin and Moczydłowska, 2012 16. Asseserium fusulentum Nagovitsin and Moczydłowska, 2012 17. Asterocapsoides fluctuensis n. sp. 18. Asterocapsoides sinensis Yin, L. and Li, 1978, emend. Xiao et al., 2014 19. Bacatisphaera baokangensis Zhou et al., 2001, emend. Xiao et al., 2014 20. Bacatisphaera sparga n. sp. 21. Bispinosphaera peregrina Liu et al., 2014 22. Briareus borealis Knoll, 1992 23. Briareus robustus n. sp. 24. Briareus vasformis n. sp. 25. Calyxia xandaros Willman, 2008 26. Cavaspina acuminata (Kolosova, 1991) Moczydłowska et al., 1993 27. Cavaspina basiconica Moczydłowska et al., 1993 28. Cavaspina conica n. sp. 29. Ceratosphaeridium glaberosum Grey, 2005 30. Crinita paucispinosa Liu et al., 2014 31. Cymatiosphaeroides forabilatus n. sp. 32. Cymatiosphaeroides kullingii Knoll, 1984, emend. Butterfield et al., 1994 33. Cymatiosphaeroides yinii Yuan and Hofmann, 1998 34. Dicrospinasphaera improcera n. sp. 35. Dicrospinasphaera zhangii Yuan & Hofmann, 1998 36. Distosphaera? corniculata n. sp. 37. Distosphaera speciosa Zhang et al., 1998, emended. 38. Eotylotopalla dactylos Zhang et al., 1998 39. Eotylotopalla delicata Yin L., 1987 40. Eotylotopalla quadrata n. sp. 41. Eotylotopalla strobilata (Faizullin, 1998; Sergeev et al., 2011 42. Ericiasphaera densispina Liu et al., 2014 43. Ericiasphaera fibrilla n. sp. 44. Ericiasphaera magna (Zhang, 1984) Zhang et al., 1998 45. Ericiasphaera rigida Zhang et al., 1998 46. Ericiasphaera cf. spjeldnaesii Vidal, 1990 47. Estrella greyae n. gen. n. sp. 48. Estrella recta n. gen. n. sp. 49. Gyalosphaeridium pulchrum Zang in Zang and Walter, 1992, emend. Grey, 2005 50. Hocosphaeridium anozos (Willman, 2008) Xiao et al., 2014 51. Hocosphaeridium dilatatum Liu et al., 2014 52. Hocosphaeridium scaberfacium Zang in Zang and Walter, 1992, emend. Liu et al., 2014 53. Knollisphaeridium bifurcatum Xiao et al., 2014 54. Knollisphaeridium coniformum n. sp. 55. Knollisphaeridium denticulatum Liu et al., 2014 56. Knollisphaeridium heliacum n. sp. 57. Knollisphaeridium longilatum Liu et al., 2014 58. Knollisphaeridium maximum (Yin L., 1987) Willman & Moczydłowska, 2008,emended 59. Knollisphaeridium obtusum Liu et al., 2014 60. Knollisphaeridium parvum Liu et al., 2014 61. Laminasphaera capillata n. gen. n. sp. 62. Membranosphaera formosa n. gen. n. sp. 63. Mengeosphaera angusta Liu et al., 2014 64. Mengeosphaera bellula Liu et al., 2014 65. Mengeosphaera chadianensis (Chen & Liu, 1986) Xiao et al., 2014 66. Mengeosphaera constricta Liu et al., 2014

Member II

★ ★ ★ ★ ★ ★ ★ ★

★ ★

★ ★ ★ ★ ★ ★ ★○ ★ ★ ★ ★ ★○ ★○ ★ ★ ★

★ ★

★ ★

Member III ★ ★ ☆● ● ☆● ★● ● ● ● ★● ● ★● ★ ★ ● ☆● ★ ● ★ ★ ★● ★● ● ● ★ ☆●

★ ★● ★● ★ ● ★● ● ★ ☆● ● ☆● ★ ● ● ★● ● ● ★ ★ ☆● ★ ☆● (continued)

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

19

Table 1. (continued) Taxon

Member II

67. Mengeosphaera flammelata n. sp. 68. Mengeosphaera gracilis Liu et al., 2014 69. Mengeosphaera latibasis Liu et al., 2014 70. Mengeosphaera lunula n. sp. 71. Mengeosphaera minima Liu et al., 2014 72. Mengeosphaera spinula Liu et al., 2014 73. Mengeosphaera stegosauriformis Liu et al., 2014 74. Mengeosphaera cf. stegosauriformis Liu et al., 2014 75. Mengeosphaera uniformis Liu et al., 2014 76. Multifronsphaeridium pelorium Zang in Zang and Walter, 1992, emend. Grey, 2005 77. Multifronsphaeridium ramosum Nagovitsin and Moczydłowska in Moczydłowska and Nagovitsin, 2012 78. Schizofusa zangwenlongii Grey, 2005 79. Sinosphaera asteriformis Liu et al., 2014 80. Sinosphaera speciosa (Zhou et al., 2001) Xiao et al., 2014 81. Sinosphaera rupina Zhang et al., 1998, emend. Liu et al., 2014 82. Tanarium acus Liu et al., 2014 83. Tanarium capitatum n. sp. 84. Tanarium conoideum Kolosova, 1991, emend. Moczydłowska et al., 1993 85. Tanarium cuspidatum (Liu et al., 2014) n. comb., emended 86. Tanarium elegans Liu et al., 2014 87. Tanarium minimum Liu et al., 2014 88. Tanarium muntense Grey, 2005 89. Tanarium paucispinosum Grey, 2005 90. Tanarium pilosiusculum Vorobeva et al., 2009 91. Tanarium pycnacanthum Grey, 2005 92. Tanarium triangularis (Liu et al., 2014) n. comb. 93. Tanarium tuberosum Moczydłowska et al., 1993 94. Tanarium uniformum n. sp. 95. Tanarium varium Liu et al., 2014 96. Tianzhushania polysiphonia Yin, C. in Yin, C. and Liu, 1988 97. Tianzhushania spinosa Yin, L. and Li, 1978, emend. Yin, C. and Liu, 1988 98. Tianzhushania sp. 99. Urasphaera fungiformis Liu et al., 2014 100. Urasphaera nupta Liu et al., 2014 101. Variomargosphaeridium floridum Nagovitsin and Moczydłowska in Moczydłowska & Nagovitsin, 2012 102. Variomargosphaeridium litoschum Zang Zang and Walter, 1992 103. Variomargosphaeridium varietatum n. sp. 104. Verrucosphaera mimima n. gen. n. sp. 105. Weissiella grandistella Vorobeva et al., 2009 106. Xenosphaera liantuoensis Yin, L. 1987, emend. Liu et al., 2014 107. Yinitianzhushania tuberifera (Yin et al., 2001) Xiao et al., 2014 108. Yinitianzhushania sp. 109. Yushengia ramispina Liu et al., 2014

★ ★ ★

★ ★ ☆ ★ ★ ★ ★ ★ ★ ★ ☆○ ☆○ ☆

★ ☆○ ☆

Member III ★● ★● ● ☆● ● ● ★ ☆● ● ● ● ★ ☆● ★● ● ★● ★ ★ ★● ● ★● ★● ★ ☆●

● ● ☆● ★ ★ ★ ★● ● ●

All species occurrence based on the present record and previously reported by Liu et al. (2013, 2014a, b). ★: recorded and described herein; ☆: recorded herein but not described; ●: reported and described previously; ○: reported previously but not described.

section increasing the biodiversity of the member II assemblage, yet their stratigraphic ranges remain to be constrained (Fig. 5).

The Jiulongwan composite section In the Jiulongwan section exposed in the southern flank of the Huangling Anticline (Figs 1B, 6), the Doushantuo Formation lies between the Nantuo Formation and the lower part of the Dengying Formation. The lower part of the Doushantuo succession is well exposed along the Douzhixian road‐cut to the north of the Wuhe village, whereas its upper part is exposed along the Zoushixian road‐cut to the northeast of the Xiangdangping village. The

Jiulongwan section comprises a composite succession from these two closely located localities. The composite succession of the Doushantuo Formation is about 181 m thick and it begins with a 4‐ m‐thick cap dolostone of member I directly overlying the Nantuo diamictite (Fig. 6). It is succeeded by the 106‐m‐thick member II, which consists of 4‐m‐thick grey, medium‐bedded, muddy dolostone with interbeds of black shale, followed by 102 m of black shale intercalated with grey, medium‐bedded muddy dolostone with ellipsoidal chert nodules. The vertical distribution and thickness of the muddy dolostone beds are irregular throughout this interval. Member III is 56 m thick and consists of an 18‐m‐ thick basal interval of grey, medium to thick‐bedded

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dolostone with abundant irregular or banded chert layers and chert nodules, an 8‐m‐thick grey or yellow–grey, finely laminated muddy dolostone, and finally 30 m of grey, banded limestone. Member IV comprises 15 m of black shale with large lenticular dolostone concretions (diameter ca. 1 m). This member is overlain with an abrupt lithologic change to the light grey, massive dolostone of the Dengying Formation and clearly defining the boundary between the two formations. The contact between the black shale of member II and the dolostone of member III is lithologically sharp and indicates a shallowing upward. In the lower part of member III at the level of 125 m (15 m above the base of member III) there is observed an erosional surface indicative of a paraconformity and sedimentological break, although the lithology is the same (Fig. 6). Abrupt lithologic change is also seen at the boundary between members III and IV. The Jiulongwan section was previously studied and correlated with other sections across the Yangtze Platform (Jiang et al. 2007, 2011; McFadden et al. 2008, 2009; Yin et al. 2009b, 2011a; Xiao et al. 2010, 2012; Zhou et al. 2012, 2017a; Zhu et al. 2013; An et al. 2015). The unconformities and flooding surfaces have been recognized at various levels within the Jiulongwan succession. The boundary between members II and III has been correlated with a mid‐Doushantuo exposure surface in the successions in the southern Yangtze Platform (e.g. Weng'an section) (Zhou & Xiao 2007; McFadden et al. 2009), or with a level within member II where a carbonate interval is overlain by black shale (Zhu et al. 2007b, 2013). However, the latter position, showing a deepening event and flooding surface at the base of the shale, does not conform to the correlation with the exposure surface in other sections. The correlation of the mid‐Doushantuo exposure surface from the Weng'an section was also proposed to be in the middle part of member II in the Jiulongwan section (Yin et al. 2011a; Zhu et al. 2013; in the latter publication, the Jiulongwan section is referred to as the Xiangdangping section in fig. 9, and alternatively named as the Toudingshi or Huangniuya section on p. 9). Jiang et al. (2011) recognized a flooding surface expressed by abrupt facies change within the lower part of ‘Member 3’ in the Jiulongwan section and correlated it with the exposure/erosional surfaces in the lower Doushantuo Formation in other sections. These authors placed another flooding surface that is recognized regionally and correlated with the upper Doushantuo unconformity at the base of ‘Member 4’.

FOSSILS AND STRATA

The boundary between the sedimentological cycles 1 and 2 suggested by McFadden et al. (2009) and marked at the level of 85 m log (no members recognized) in the Jiulongwan section (Xiao et al. 2012) would correspond to the middle part of member II. This is not clearly seen herein, and sharp lithologic change is in contrast observed at the base of member III (Fig. 6). Xiao et al. (2012) considered the boundary between members II and III to be transitional but it is shown to be a sharp lithologic contact between intervals of shale and dolostone (Fig. 6). Zhou et al. (2017a) emphasized that the boundaries between all members (I–IV) and with the overlying Dengying Formation and its lowermost Hamajing Member are at sharp lithologic contacts and additional abrupt change in lithology is observed between the dolostone and succeeding limestone interval within member III. We do not observe any major shift in lithology or any level that could be recognized as correlative to the mid‐Doushantuo unconformity within member II but the boundary between members II and III is a candidate for paraconformity. It shows a major depositional change and shallowing event. The erosional surface is recognized at the level 125 m in the section (Fig. 6) and it seems to be contemporaneous to the exposure that is recorded in other sections of the Yangtze Gorges area (Zhu et al. 2013). The flooding surface marking the lower boundary of member IV is recognized in the Jiulongwan section and in the southern area of the Huangling Anticline (Jiang et al. 2011), whereas in the eastern area member IV is absent showing the paraconformity and stratigraphic hiatus and indicating tectonic instability of the platform margin at the time. Microfossils in the Jiulongwan succession were previously studied (Tang et al. 2006; Zhou et al. 2007; McFadden et al. 2008, 2009; Xie et al. 2008; Yin et al. 2009a, b, 2011a), and we add 5 new species to the record and extend ranges of other species. Zhou et al. (2007) and Xie et al. (2008) have reported microfossils from the lower part of member II (interval at 10−70 m above the base of Doushantuo Formation), including Cymatiosphaeroides kullingii (identified here as Dicrospinasphaera improcera n. sp.), Ericiasphaera magna, E. sparsa, E. spjeldnaesii, Meghystrichosphaeridium chadianensis (= Mengeosphaera chadianensis), M. magnificum (identified here as Appendisphaera grandis), Papillomembrana sp., Tianzhushania spinosa and T. tuberifera (transferred here to Yinitianzhushania tuberifera). Additionally, large spherical microfossils Megasphaera ornata and Megaclonophycus onustus that are interpreted to be metazoan embryos, and multicellular algae Sarcinophycus papiloformis and S. radiates occur with acritarchs.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

McFadden et al. (2008) listed microfossil occurrence in the Jiulongwan section in member II at 10– 50 m and they followed the taxonomic assignment according to Zhang et al. (1998b) with the caution of the needed revision for some taxa. Subsequently, McFadden et al. (2009) revised a few species (Tanarium conoideum, Cavaspina acuminata) and recognized Papillomembrana compta in the assemblage. They reported the presence of numerous species from the lower part of member II (interval 10–60 m above the base of Doushantuo Formation) in this section but did not illustrate the microfossils. The assemblage included Apodastoides basileus, Asterocapsoides sinensis, Cymatiosphaeroides kullingii, Cavaspina acuminata, Echinosphaeridium maximum (=Knollisphaeridium maximum), Eotylotopalla dactylos, E. delicata, Ericiasphaera magna, E. rigida, E. sparsa, E. spjeldnaesii, Meghystrichosphaeridium chadianensis (=Mengeosphaera chadianensis), M. magnificum (=Appendisphaera grandis), Papillomembrana compta, Polygonium cratum (=Tanarium tuberosum), Tanarium conoideum and Tianzhushania spinosa. The species Meghystrichosphaeridium gracilentum and Meghystrichosphaeridium ‘perfectum’ in the assemblage are considered invalid taxa, and the latter species includes Cavaspina basiconica and Mengeosphaera bellula. These cited records are more diverse taxonomically than the present assemblage although some species may be synonymous with other species but not being illustrated they could not be evaluated. We do not revise the taxonomic attribution of reported species but significant for the biostratigraphic correlation are those commonly occurring species, such as Appendisphaera grandis, Cavaspina acuminata, C. basiconica and Papillomembrana compta, if confirmed to be present. Yin, C. et al. (2009a) preliminarily described several species in the Jiulongwan section, e.g. Tianzhushania spinosa, T. polysiphonia, T. ornata (=Yinitianzhushania tuberifera), Eotylotopalla delicata, Tanarium conoideum (transferred by Liu et al. 2014b to Hocosphaeridium scaberfacium) and Echinosphaeridium maximum (= Knollisphaeridium maximum). These authors distinguished two different assemblages which are recorded in members II and III, respectively. Yin, C. et al. (2011a) mentioned the occurrence of the ‘lower assemblage’ in member II in this section and listed characteristic species, including certain invalid species, yet without their stratigraphic position. The significance of this record is by the presence of Tianzhushania spinosa and T. ornata (= Yinitianzhushania tuberifera) in the lowermost member II at the intervals of 13–19 m and 27–32 m.

21

Some macrofossils have been reported from the Jiulongwan succession, including chuarids and some uncertain trace fossils from the level 35 m above the base of the Doushantuo Formation, and one multicellular, branching alga Enteromorphites sp. from 60 m above the base of the Doushantuo Formation (Tang et al. 2006). In the present study, 12 chert horizons from member II yielded microfossils that are attributed to 9 genera and 12 species including 5 new species (Fig. 6). Species Tianzhushania spinosa, T. polysiphonia and Yinitianzhushania tuberifera were diagnostic of the assemblage zone from the lower part of member II (Liu et al. 2014b). Species recorded for the first time in the section are Distosphaera speciosa, Dicrospinasphaera zhangii and Weissiella grandistella. The first appearance datum (FAD) of new species, Dicrospinasphaera improcera, Estrella greyae and Knollisphaeridium coniformum, is recognized at the level 12 m. Four chert horizons from the lower member III were studied but yielded only un‐diagnostic Leiosphaeridia spp. and filamentous cyanobacterial microfossils of Siphonophycus spp.

The Chenjiayuanzi section In the Chenjiayuanzi section (Figs 1B, 7), the Doushantuo succession is exposed along a trail on the southern hillside of the Chenjiayuanzi village, and it has been studied by Liu et al. (2014a). This section is very close to the Tianjiayuanzi type section of the Doushantuo Formation (Wang et al. 1998; Zhu et al. 2003). The Doushantuo Formation is 180 m thick and its basal 2‐m‐thick cap dolostone of member I overlies the Nantuo diamictite with a paraconformity. The lowermost 0.5 m of the cap dolostone is cut by irregular quartz veins and consists of stromatactis‐like cavities suggesting strong alteration and erosion. It is succeeded by a 1‐m‐thick, grey, thick‐bedded, laminated microcrystalline dolostone with tepee‐like structures, followed by 0.5 m of grey medium‐ to thick‐bedded laminated dolostone. Member II is a 103‐m‐thick succession of black shale interbedded with muddy dolostone with chert nodules. It consists of 7 m of black shale with thin‐ bedded muddy dolostone at the base that is succeeded by 50 m of dolostone intercalated with muddy dolostone and a thin layer of black shale, which contains abundant black chert nodules. This interval is followed by 46 m of black shale intercalated with thin‐ to medium‐bedded muddy dolostone with a few chert nodules in the upper part of member II. The shale succession of the upper part of member II is partly covered.

22

P. Liu & M. Moczydłowska

Member III is a 55‐m‐thick, light grey, medium‐ to thick‐bedded dolostone intercalated with a few thin‐ bedded muddy dolostone beds, and it forms a steep cliff in the area. The lower part of member III contains abundant black chert lenticular layers and chert nodules, whereas the upper part contains abundant black chert bands, small nodules, and pale grey, silicified oolitic dolostone (10–50 cm thick). Member IV is formed by 20 m of black shale with lenticular dolostone layers and concretions, which is overlain by medium‐bedded dolostone of the Dengying Formation. As argued for the Jiuqunao section and recognized in a regional scale, also here the lower boundary of the Doushantuo Formation at its basal cap carbonate is paraconformable with the Nantuo Formation diamictite. The boundaries of all members in the Chenjiayuanzi section are defined at levels of abrupt change between shale and dolostone lithofacies (Liu et al. 2014a). These levels indicate transgressive‐ regressive cycles. Flooding surfaces are at the base of members II and IV, as well as in the middle part of member II (Fig. 7). An erosional surface at the level 152 m (41 m above the base of member III) is recognized herein (Fig. 7). The lithology does not change throughout member III but the chert nodules are absent above the erosional surface. It is not certain which stratigraphic level could coincide with the regional unconformity within the mid‐Doushantuo Formation that is recognized in other sections across the Yangtze Platform area (Zhu et al. 2007b, 2013; Jiang et al. 2011). A shallowing event in the uppermost member II marked by the beginning of dolomite deposition that continued throughout member III is a possible correlative level (Fig. 7). Alternatively, it could be the newly recognized erosional surface in the upper part of member III. Previously, microfossils have been studied in this section and grouped into two distinct assemblages (Liu et al. 2014a). Some of those species are revised taxonomically and Cymatiosphaeroides kullingii is transferred to Dicrospinasphaera improcera n. sp., Appendisphaera dilutopila is synonymous to A. tenuis, and Mengeosphaera triangularis is recognized as a new combination of Tanarium triangularis (see under palaeontological descriptions). Alicesphaeridium lappaceoum is synonymized with A. medusoidum. The plexus of genera Tianzhushania and Yinitianzhushania will be treated taxonomically elsewhere, but their species are newly recorded in more stratigraphic levels (Fig. 7). Numerous species are newly recovered, such as Appendisphaera grandis, A. setosa, A. tenuis, Asseserium diversum, A. fusulentum, Calyxia xandaros, Bacatisphaera baokangensis,

FOSSILS AND STRATA

B. sparga, Cavaspina acuminata, Eotylotopalla delicata, Gyalosphaeridium pulchrum, Mengeosphaera constricta, Tanarium cuspidatum, T. paucispinosum and Variomargosphaeridium litoschum. Several new taxa are recognized in both members II and III increasing the taxonomic diversity of the assemblages. Other species recovered in the Chenjiayuanzi section by Liu et al. (2014a, fig. 6), including Appendisphaera anguina, A. clava, Cymatiosphaeroides yinii, Hocosphaeridium scaberfacium, Knollisphaeridium triangulum, Mengeosphaera bellula, M. constricta, M. spinula and Schizofusa zangwenlongii, are not repeated herein. The revised and extended list of species is shown in Figure 7. In the present study, 27 chert horizons were examined (Fig. 7). All 13 chert horizons from member II and 12 among 14 studied from member III contain acanthomorphic acritarchs. Altogether, 26 genera and 48 species are identified and the two members contain distinct assemblages. However, three species that appear in the lower assemblage of member II (Appendisphaera grandis, Eotylotopalla dactylos and E. delicata), have wider stratigraphic ranges that extend into member III and the upper assemblage. This record poses the need to revise the taxonomic content and range of the upper assemblage, which has been previously thought to be restricted to member III (Liu et al. 2014a, b; see chapter Biostratigraphy). The FAD of Appendisphaera grandis is recognized in the Wangfenggang section at the level 9.4 m (see below), and the species occurs throughout members II and III (Fig. 15). Species restricted to member II in their occurrence are Tianzhushania spinosa, T. polysiphonia, Yinitianzhushania tuberifera and Briareus borealis. The ranges of newly described species from this member, Dicrospinasphaera improcera n. sp. and Knollisphaeridium coniformum n. sp. await to be fully recognized, but the FAD of K. coniformum n. sp. coincides with this of T. spinosa and Y. tuberifera, whereas the FAD of Distosphaera improcera n. sp. is at the level 12 m. The FAD of Distosphaera speciosa is recorded at 9.5 m and the species extends through members II and III. All species recovered in member II are very rare (a few specimens) with the exception of Tianzhushania spinosa (more than 200 specimens). The member III assemblage is taxonomically diverse but ranges through a short interval of strata at 128–152 m (24‐m interval) and is restricted to the presence of chert nodules in dolostone. The erosional surface recognized at the level 152 m terminates the distribution of the chert nodules and thus microfossils but not their true stratigraphic ranges which are

FOSSILS AND STRATA

Fig. 15. The chart of stratigraphic ranges of microfossil species studied here in the Doushantuo Formation and established by their FAD and LAD. The approximate ages of the FAD and LAD are estimated from the isotopic ages of strata containing these species or are interpolated from the ages of global events, such as the Gaskiers glaciation at ca. 580 Ma (Ogg et al. 2016) and the appearance of the Ediacara‐type biota in Australia at ca. 565 Ma (Grey 2005).

Ediacaran microfossils from the Doushantuo Formation

23

24

P. Liu & M. Moczydłowska

known in other sections to be wider. Previously distinguished Hocosphaeridium anozos–H. scaberfacium assemblage in member III (Liu et al. 2013, 2014a, b) has to be redefined because of the extended ranges of certain species into member II, including the nominal H. anozos (see under Biostratigraphy). The carbon isotope δ13C profile of this section shows remarkable fluctuations with two positive excursions and three negative excursions (Liu et al. 2014a; Fig. 7). These excursions are, in ascending order: (1) a negative δ13C excursion (EN1 or CANCE; CAp carbonate Negative Carbon isotope Excursion; Zhu et al. 2007a) in the cap carbonate of member I; (2) a prolonged positive δ13C excursion (EP1 that is Ediacaran Positive excursion 1) in the lower part of member II; (3) a negative δ13C excursion (EN2 or BAINCE) in the upper part of member II, although the δ13C values in this stratigraphic interval are not stable and are admixed with some positive values; (4) a positive δ13C excursion (EP2) in the lower and middle part of member III, apart from four samples with negative δ13C values which may be diagenetically altered as indicated by δ18O values and Mn and Sr data; and (5) a remarkable negative δ13C excursion (EN3 or DOUNCE) from the upper part of the Member III to the basal part of the Dengying Formation. The observed shifts between negative and positive δ13C values occur in the levels of abrupt lithologic change and the presence of unconformity and probable paraconformities. This is evident at the stratigraphic level of the erosional surface at the level 152 m and unconformity or paraconformity (strata are parallel across the erosional surface), leading to the negative EN3 excursion. The same is inferred at the level of shallowing event at 70 m and referred to the beginning of the negative EN2 excursion. The negative excursion EN1 in the cap carbonate coincides with the inferred herein paraconformity at the base of the Ediacaran System and, as aforementioned, 1‐m‐thick interval of alteration and erosion with stromatactis‐like cavities recognized in the Chenjiayuanzi section.

The Nantuocun section The Nantuocun section (Fig. 8) records a fragmentarily exposed 36‐m‐thick succession that is herein attributed to the middle part of member II. The section is exposed along the road‐cut and consists of alternating grey, medium‐ to thick‐bedded dolostone and thin‐ to medium‐bedded muddy dolostone, all with chert nodules (Fig. 8). The Nantuocun section has been reported in stratocolumn by Xiao (2004) and adopted from Zhang

FOSSILS AND STRATA

et al. (1998b) as overlying the Nantuo Formation diamictite. However, there is no exposed contact between these two successions and thus no direct stratigraphic reference to estimate the relative age of the Doushantuo interval in the Nantuocun section. The stratigraphic column adopted as the Nantuocun section was the composite, generalized or idealized succession for the Yangtze Gorges area, and correlated with the Weng'an section in the southern Yangtze Platform (Zhang et al. 1998b), and referred to the upper Doushantuo Formation (Xiao 2004). This is refuted herein and the succession is referred to the lower Doushantuo Formation (see below). Xiao (2004) described microfossils from the Nantuocun section consisting of multicellular algae Sarcinophycus papilloformis and Wengania minuta, cyanobacteria Obruchevella and Salome, and acanthomorphic acritarchs Dicrospinasphaera zhangii and Meghystrichosphaeridium chadianensis, referring their occurrence to the upper Doushantuo Formation yet without citing their position in the stratigraphic succession. The latter species has been transferred to Mengeosphaera minima (Liu et al. 2014b) and is represented by a single, poorly preserved specimen (Xiao 2004, fig. 3.8, 9), which is not qualified for any certain identification; therefore, we do not include it in the fossil content of the Nantuocun section. Dicrospinasphaera zhangii is well‐preserved but its occurrence is not known in any detail in the succession, and therefore is neither shown in Figure 8. The stratigraphic position of the Nantuocun succession is re‐evaluated herein and attributed to the lower Doushantuo Formation (member II). This is based on the occurrence of age‐diagnostic species Tianzhushania spinosa that is known in the Yangtze Gorges area in the lower part of member II (Liu et al. 2013, 2014b). In our study, among 14 examined chert horizons 12 appeared fossiliferous and consist of 8 genera and 10 species including five new species (Fig. 8). The new species await further recognition of their geographical distribution and stratigraphic ranges, whereas species known from the Yangtze Platform area include Distosphaera spinosa, Ericiasphaera magna and Mengeosphaera gracilis. Appendisphaera grandis is the only species in the assemblage having cosmopolitan distribution on other palaeocontinents as in numerous sections on the Yangtze Platform.

The Wangfenggang section (= Liantuo) The Wangfenggang section (Fig. 9) is exposed along a trail on the northern hillside of the Liantuo Bridge/ Liantuo village, and this section has also been called

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

the Liantuo section (Zhou et al. 2007). The Doushantuo Formation basal 3‐m‐thick cap dolostone of the member I overlies the Nantuo Formation and is succeeded with a sharp lithologic contact by the black shale interval of member II. Member II consists of an 11‐m‐thick black shale with interbeds of grey, thin‐ to medium‐bedded muddy dolostone at the lowermost part, and a 6‐m‐thick muddy dolostone, both intervals comprising chert nodules. Overlying is 67 m of grey, massive medium‐ to thick‐ bedded dolostone interbedded with muddy dolostone with abundant black chert nodules (within the measured interval of 20–87 m). The above 38 m of the section is poorly exposed and the succeeding interval of 8 m black shale is attributed to the uppermost part of member II. The lower boundary of member III is at the level of abrupt lithofacies change into a dolomitic succession. The basal member III comprises 3 m of muddy dolostone and then a succession of grey, medium‐ to thick‐bedded dolostone with chert nodules, which is only partially exposed. The stratigraphic column of the Doushantuo Formation in this section has been provided by Yin, C. et al. (2011a) and Liu et al. (2013, 2014b), and we follow it herein. The Wangfenggang succession has been studied in various stratigraphic intervals for microfossils but they were not systematically described (Yin et al. 2007a, 2011a; Zhou et al. 2007; McFadden et al. 2009; Liu et al. 2013). Zhou et al. (2007) provided a list of species from the synonymous section named Liantuo from the lower member II interval of 34 m but without geological succession. The reported species are Tianzhushania spinosa and Ericiasphaera rigida, which are recorded also herein, and E. spjeldnaesii, ‘Goniosphaeridium’ acuminatum (= Cavaspina acuminata) and ‘Meghystrichosphaeridium gracilentum’, which are not recovered in our studies. The description of a new combination of species ‘gracilentum’ by Zhang et al. (1998b, fig. 9.13, 14) as Meghystrichosphaeridium is non‐diagnostic and the illustrated specimens are likely Tanarium pycnacanthum Grey, 2005. Meghystrichosphaeridium gracilentum (Yin and Liu 1988; Zhang et al., 1998b) was subsequently attributed to Tanarium gracilentum and Solisphaeridium gracilentum (Yin, C. 1999; Yin, C. et al., 2007; McFadden et al. 2009). The species ‘gracilentum’ is poorly defined and illustrated and it has been transferred between various genera, and in fact may comprise various species. McFadden et al. (2009) reported schematically the distribution of microfossils in a 40‐m‐thick interval in the lowermost part of the succession (10–50 m in their measured section) and referred it to the lower Doushantuo sedimentological cycle 1. The cited species are the same as listed by Zhou et al. (2007) and are

25

additionally recorded from the upper stratigraphic level at 50 m, and Cavaspina acuminata is revised taxonomically. Some of them are also recorded here but in member III, such as Echinosphaeridium maximum = Knollisphaeridium maximum, Tanarium conoideum, Meghystrichosphaeridium chadianensis and M. ‘perfectum’ (invalid taxon, which may comprise Cavaspina basiconica and Mengeosphaera bellula, recorded herein). The species Ericiasphaera sparsa is not recovered in our study. Liu et al. (2013) listed the species occurring in members II and III but did not illustrate or describe them, and subsequently, this record was revised by Liu et al. (2014b). Liu et al. (2014b) studied in detail the taxonomy of microfossils from member III. We extend this record by adding Appendisphaera grandis and revise taxonomically certain species by transferring Appendisphaera barbata? to A. tabifica, and A. magnifica to A. grandis. Many other species from member III are newly recovered and the compiled and revised list of species is provided in Fig. 9. Our study was focused on member II and among 21 chert horizons 20 are fossiliferous recording 13 genera and 20 species, including 5 newly described species (Fig. 9). The microfossil assemblage in the lower member II is diverse taxonomically and consists of species known in other sections on the Yangtze Platform. Tianzhushania spinosa is recorded throughout the interval containing microfossils. The most important species observed for interregional correlation are Appendisphaera grandis, A. tabifica, A. tenuis, Tanarium paucispinosum, T. pilosiusculum and Weissiella grandistella. The FAD for Appendisphaera grandis is at 9.4 m. This is also the FAD for Weissiella grandistella and Tanarium pilosiusculum, and for species occurring only in the Yangtze Platform, such as Distosphaera speciosa, Ericiasphaera rigida, Mengeosphaera gracilis and the new genus and species Estrella greyae. Diagnostic for the regional Chinese zonation species Tianzhushania spinosa and Yinitianzhushania tuberifera appear at 9.4 m, T. polysiphonia and Ericiasphaera magna at ca. 10.3 m, and Mengeosphaera chadianensis at 11.7 m, confirming their lowermost occurrences in other sections.

The Niuping composite section The Niuping section (Fig. 10) is well exposed on the hillside (lower part) and in the road‐cut (upper part) near the Niuping village and is a composite succession of the Doushantuo Formation. The stratigraphic succession has been described by Yin, C. et al. (2011a) and taxonomically studied in detail by Liu et al. (2013, 2014b). The Doushantuo Formation here is over 190 m and consists of members I, II and

26

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III, whereas member IV is missing and indicates a stratigraphic gap in this section. The Doushantuo succession comprises 4.7 m of cap dolostone of member I that overlies the Nantuo diamictite. The basal 1 m is a brecciated massive dolomite with irregular quartz veins, which is followed by dolomite with large‐scale tepee structures, and laminated dolomite at the top. The contact between member I with the Nantuo Formation diamictite is discontinuous, as shown by the described features, and marks the paraconformity. In other sections in the Yangtze Gorges area, the unconformity at the base of the Doushantuo Formation has been recognized at the base of sequence 1 (S1) and sequence boundary 1 (SB1) (Zhu et al. 2007b, 2013; McFadden et al. 2009; Jiang et al. 2011; Zhou et al. 2017a). Member II in the Niuping section is a 145‐m‐thick interval and its lower and upper boundaries are marked by abrupt changes in lithology. It consists of 16 m of black dolomitic shale overlain by 19 m of thin‐bedded muddy dolomite with phosphatic chert nodules. The dolomite beds become thicker at 35 m above the formation base. A 50‐m‐thick dolomite with abundant phosphatic chert nodules in the middle part of member II forms a cliff. The succeeding 70 m of black shale intercalated with muddy dolomite containing phosphatic chert nodules occurs at 80–150 m within the measured section in the upper part of member II. Member III is a 50‐m‐thick dolomite with abundant chert nodules. Its lower boundary is defined at the level of lithologic change from thin‐bedded muddy dolostone (member II) to thick‐bedded massive dolostone (member III). The excellent exposure in this section clearly shows that the black shale of member IV is missing here, and greyish, massive crystallized dolostone of the Dengying Formation overlies the grey dolostone with chert nodules interval of member III. The boundaries between members I, II and III in the Niuping succession are at sharp contacts. The lower boundary of the Dengying Formation is at the base of the massive crystallized dolostone and in contact with the underlying layer of muddy dolomite with chert nodules of member III. This is the level of paraconformity between the two formations that involves the stratigraphic hiatus that is equivalent to the depositional time of member IV in other sections. This is evident by comparison with other sections where member IV is present and overlain by the Dengying Formation, and where the member III dolostone or limestone intervals of similar thicknesses (55 m and 56 m in the Chenjiayuanzi and Jiulongwan sections, respectively) underlie the shale of

FOSSILS AND STRATA

member IV. Even in the Jiuqunao (=Jijiawan) succession, where member III interval is thinner (ca. 30 m thick), as is the entire Doushantuo Formation (105 m thick), all members are present beneath the Dengying Formation. In a regional scale of the Yangtze Gorges area, the lack of member IV in some sections has been inferred to show the lithofacies change in the lateral extension between the sections and being ‘not developed’ (Jiang et al. 2011; Yin, C. et al. 2011a; Xiao et al. 2012). Liu et al. (2014b) interpreted a one‐metre‐ thick, thin‐bedded siliceous layer at the top of member III as a possible chronostratigraphic marker, equivalent to member IV in the Niuping section. Zhou et al. (2017a) suggested the presence of a cryptic disconformity at the boundary between the Doushantuo and Dengying formations in the Niuping section, and in general in the eastern region of Yangtze Gorges, indicated by the lack of black shale interval within the uppermost Doushantuo Formation that is well developed in most regions. Because the strata dip is not different between the formations, we postulate the presence of a paraconformity concealing a stratigraphic hiatus of uncertain time duration between the two formations. The carbon isotope curve in the Niuping section (Yin, C. et al. 2011a; Liu et al. 2013, 2014b) does not show any significant fluctuations and is persistently positive throughout the Doushantuo members II and III to the lower Dengying Formation. The only exception is a one sample level at 128 m with a negative δ13C value. This is in contrast to δ13C values recorded in the uppermost member IV in the Chenjiayuanzi section (EN3 or DOUNCE excursion in Liu et al. 2014a; Fig. 10) and in other sections (Jiulongwan, Baiguoyuan, Xiangerwan, Qinglinkou, Zimaping, Zhengjiatang), which are highly negative (Jiang et al. 2007; Zhu et al. 2013; An et al. 2015; Zhou et al. 2017a). This negative carbon anomaly in the Yangtze Gorges area has been correlated with the Shuram‐Wonoka anomaly recorded globally (Grey et al. 2003; Fike et al. 2006; Jiang et al. 2007, 2011; Zhou & Xiao 2007; Zhu et al. 2007b, 2013; An et al. 2015; Zhou et al. 2017a). The lack of the Shuram‐ Wonoka anomaly record is taken as an additional evidence for inferring a stratigraphic hiatus in the Niuping section because of the missing sediment interval that would be equivalent to this part of the stratigraphic succession. The hiatus is also recognized in the Dishuiyan and Liuhuiwan sections (see below) on the ground of missing portions of the sedimentary succession. The carbon isotope negative excursion in the cap dolostone of member I in the Niuping succession is typical of all Doushantuo Formation sections.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Another negative excursion recorded at a narrow interval (1 sampled level) in the uppermost member II coincides with the level of appearance of dolostone beds with chert nodules above the shale interval. This level has been correlated with the EN2 excursion (Liu et al. 2013). Yin, C. et al. (2011a) interpreted this minor negative δ13C shift to occur across the erosional surface. They recognized another erosional surface in the lower member II (at the 62 m level measured here) also with minor δ13C shift. It appears to be a consistent pattern in δ13C negative excursions to coincide with unconformities or paraconformities in sedimentological successions. The examples of such coupling are also shown in the Yangtze Gorges and Weng'an sections (Zhu et al. 2007b, figs 5, 11; Zhou et al. 2017b, p. 1194, fig. 2), and in the composite Doushantuo Formation profile (Zhou & Xiao 2007, fig. 6), as in other sections (Jiang et al. 2007). Microfossil occurrence in the Niuping succession was preliminarily reported by Yin, C. et al. (2011a) in member II (Tianzhushania spinosa, T. ornata=Yinitianzhushania tuberifera) and member III (first acanthomorphic species and spheroidal taxa, yet unidentified). Liu et al. (2013) reported a few species from both members II and III, and the member III interval has been subsequently studied in taxonomic and stratigraphic detail by Liu et al. (2014b). The list of previously recorded and taxonomically revised species is combined with the newly recovered taxa from the present study (Fig. 10). The additional species recovered in member III is Eotylotopalla strobilata, whereas Appendisphaera grandis was previously attributed to A. magnifica and Tanarium tuberosum to T. obesum. Altogether we record 20 genera and 59 species including 7 newly described. In the present investigation of member II, 11 chert horizons yielded 13 genera and 21 species (Fig. 10). The FAD of the newly recognized species in member II has to be confirmed by further studies. In the assemblage, Tianzhushania spinosa is numerous and extends across the studied interval at ca. 23–108 m showing its widest recorded range, whereas other species are very rare. The taxonomic diversity is high and seven new species are identified: Appendisphaera clustera, Dicrospinasphaera improcera, Eotylotopalla quadrata, Estrella greyae, Knollisphaeridium coniformum, Mengeosphaera flammelata and Tanarium capitatum. The species Hocosphaeridium anozos is recorded in the lowermost chert horizon (23 m) and for the first time in member II. This species was a nominal species of the Tanarium conoideum–Hocosphaeridium scaberfacium–Hocosphaeridium anozos assemblage in the Yangtze Gorges area and was defining the second (or upper) zone that has been established

27

in member III of the upper Doushantuo Formation (Liu et al. 2013, 2014a, b). The new record of H. anozos in the basal member II requires the revision of the second assemblage and biozone taxonomic content and it refutes the species anozos as the index taxon defining it. The stratigraphic range of this species extends through member II and III (Fig. 10). The species H. anozos was reported to occur through member II in the Siduping section (Hawkins et al. 2017). However, the illustrated specimen (Hawkins et al. 2017, fig. 7E, F) shows a single process with hooked tip among all others that are long straight conical processes, and this identification is uncertain. A single hooked tip is the result of taphonomic preservation and not a persistent feature of the species.

The northern Xiaofenghe section The two Xiaofenghe sections, northern and southern, record substantial portions of the Doushantuo Formation and together the succession exceeds 220 m in thickness by correlating the sections along the level of the shale layer at the base of the limestone interval (within member II; Figs 11, 12; see also Zhu et al. 2007b, 2013). These two Doushantuo successions are partial and neither exhibit the uppermost member III or member IV nor the contact with the Dengying Formation. The composite succession has been compiled from the two sections as the Xiaofenghe section (Yin, L. et al. 2007b; Zhu et al. 2007b; McFadden et al. 2009; Liu et al. 2014b) but actually there is no single section through the Doushantuo Formation and no contact is known with the Dengying Formation. The northern Xiaofenghe section in the eastern flank of the Huangling Anticline (Fig. 11) is the same section described as the northern Xiaofenghe (NXF) by Xiao et al. (2012), and the Xiaofenghe section A (north hillside) by Zhu et al. (2013). The lithostratigraphic logs of the section were measured from different reference points and the lithological descriptions differed slightly between various authors, whereas the members were recognized only recently (Liu et al. 2014b). This section was incorporated as a lower part of the composite succession of the Doushantuo Formation in the Xiaofenghe section (Yin, L. et al. 2007b; Zhu et al. 2007b; Liu et al. 2014b). The here measured 145‐m‐thick succession, consisting of member I and the lower–middle part of the member II, is well exposed along a trail on the northern hillside of the Xiaofenghe village. The upper portion of the Doushantuo Formation is exposed in the southern Xiaofenghe section recording the upper member II and the lower member III succession (see below).

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In the northern Xiaofenghe section, the basal 4‐m‐ thick cap dolostone of member I overlies the Nantuo diamictite and is succeeded by member II that begins with a 21 m of black shale intercalated with muddy dolostone and comprising one layer of phosphorite in its upper part (Fig. 11). Overlying this interval is 84 m of grey, medium‐ to thick‐bedded dolostone intercalated with medium‐bedded muddy dolostone containing abundant black chert nodules. The dolostone interval is separated by a 1‐m‐thick black shale layer from the overlying 35 m of grey, massive limestone with chert nodules and chert bands. The top of the succession is not exposed. The boundaries of the two members (I–II) recorded here are at abrupt lithologic change (Fig. 11). The boundary between the Nantuo diamictite and cap dolostone is at a regional unconformity level (Zhu et al. 2007b) or paraconformity as inferred herein (see above). The lower boundary of member II is marked by the level of abrupt appearance of black shale overlying the cap dolostone and denotes the prograding transgression event. Sharp lithologic contact is also observed at the 25 m level between an interval of black shale and dolostone that extends upward to 110 m. This lithologic change occurring above a distinct phosphorite layer, indicates the shallowing event and a parasequence boundary. An abrupt lithologic change is also evident at the interval of 1‐m‐ thick black shale that separates the dolostone from the overlying limestone succession. This shale bed is a local marker horizon for the correlation of the northern and southern Xiaofenghe sections. It shows a short episode of deepening in the long‐lasting carbonate shelf depositional regime of member II. Zhu et al. (2007b) described the Xiaofenghe section as a composite Doushantuo Formation succession from two outcrops (northern, the lower portion, and southern, the upper portion of the formation) and with the overlying Dengying Formation. However, the Dengying Formation is not exposed in the upper portion of the section (see Zhu et al. 2013, herein). Subsequently, the two Xiaofenghe sections were studied for the chemostratigraphic carbon isotope‐based correlation (Zhu et al. 2013) and the upper Doushantuo Formation in the southern section B was mentioned to be affected by faulting, having a repeated interval. The boundary with the Dengying Formation is not easily recognizable. Significant and correlative unconformities have been recognized in both sections of the Doushantuo Formation that are at 87 m in the northern section (Xiaofenghe section A, north hillside; lower part of the formation) and at 0 m in the southern section (Xiaofenghe section B, southern hillside; higher part

FOSSILS AND STRATA

of the formation) (Zhu et al. 2007b, 2013). These unconformities are marked between the dolostone interval and the overlying silty and muddy dolostone with phosphorite nodules. The unconformity at 87 m in the northern section is not so clearly exposed as is the erosional surface in the correlative southern section (Zhu et al. 2013). We have not observed the erosional surfaces in the northern section. The interval at 87 m in this section may alternatively indicate a shallowing episode and not the erosional exposure. In the southern section, we have recognized the level of the erosional surface at c. –19 m in member II (Fig. 11). This is however puzzling because both northern and southern sections are closely located and expose correlative portions of the Doushantuo Formation. Xiao et al. (2012) identified in the northern Xiaofenghe section a sharp lithologic change at 96 m in their measured log between the interval of phosphatic‐dolomite wackestone–packstone and the dolomitic mudstone and interpreted it as a flooding surface. Because of differences in the measured logs, we approximately correlate their level of flooding surface with the level above the unconformity suggested by Zhu et al. (2013). Xiao et al. (2012) further concluded that the three sedimentological cycles (distinguished by McFadden et al. 2009) and the sequence boundaries or erosion surfaces in the Xiaofenghe sections are poorly recognized and have been placed at different levels in lithostratigraphic columns. These authors considered that there is a single erosional surface in the Doushantuo Formation in both northern and southern sections that is correlated, and it occurs at the level of 96 m in their log (Xiao et al. 2012, p. 135). The δ13C profile of the Xiaofenghe succession shows a significant negative excursion in the cap dolostone (member I) and typically as recognized in other sections, and at the lower part of member II, which is rather erratic and recorded in two samples. Otherwise, positive values persist throughout member II (Xiao et al. 2012; Liu et al. 2013; Zhu et al. 2013). In previous studies (Yin, L. et al. 2007b, 2008, 2011b; McFadden et al. 2009), microfossils from this section (as a part of the composite Xiaofenghe section), have been reported accounting for 19 or 21 species and some additional fossils only identified to the genus level (Yin, L. et al. 2007b, fig. 2; McFadden et al. 2009, fig. 2E). However, microfossils were listed and not systematically described or illustrated, with the exception of Tianzhushania spinosa (Yin, L. et al. 2007b, whereas two other species are not recognizable at the given magnification). Yin, L. et al. (2008) reported two new species Tianzhushania fissura and

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

T. conferta from this section but both species were subsequently attributed to T. spinosa by Xiao et al. (2014a). Studies by Liu et al. (2013, 2014b) dealt with microfossils from member III of the southern section, which has been also incorporated into their composite Xiaofenghe section (see below). The 10 here studied chert horizons from member II yielded microfossils attributed to 15 genera and 22 species, including 9 new species: Appendisphaera clustera, Cavaspina conica, Cymatiosphaeroides forabilatus, Dicrospinasphaera improcera, Eotylotopalla quadrata, Estrella greyae, E. recta, Membranosphaera formosa, Tanarium capitatum, T. cuspidatum (Fig. 11). The species Tianzhushania spinosa, T. polysiphonia and Yinitianzhushania tuberifera are restricted to member II in the Yangtze Gorges area (Liu et al. 2014b), as are eight new species (see above with the exception of Tanarium capitatum n. sp.) recorded at present. The other species in the assemblage (listed in Fig. 11) are known from both members II and III.

The southern Xiaofenghe section The southern Xiaofenghe section (Fig. 12) is closely located to the northern Xiaofenghe section and is well exposed along the road‐cut in the Xiaofenghe village (Zhu et al. 2013; Liu et al. 2014b). It is the same section as Xiaofenghe section B (south hillside) described by Zhu et al. (2013). The two successions of the Doushantuo Formation, southern and northern, are on the opposite hillsides across the valley. The here measured succession is 110 m thick, fragmentarily outcropped and without the sedimentological continuation neither with the Nantuo nor the Dengying formations. It extends from the upper member II to the lower member III (Fig. 12). The succession referred to member II consists of 30 m of grey, medium‐ to thick‐bedded dolostone with black chert nodules, followed by 1 m of black, dolomitic shale with abundant small chert nodules. This bed is a lithostratigraphic reference level at 0 m (Fig. 12). This bed also marks the lithologic change between the underlying dolostone and the succeeding limestone (as in the northern section at the level 110 m; Fig. 11). The succeeding interval is 13 m of grey, thick‐bedded limestone with abundant black chert nodules in its lower part. The sharp lithologic contact exists with the overlying 22 m of black shale that is intercalated with thin‐ to medium‐bedded muddy dolostone layers. This shale interval is discontinuously exposed and constitutes the uppermost part of member II. Similarly, an abrupt lithologic change into dolomite at the lower boundary of member III is observed at 35 m. The basal member III consists of 16 m of grey, medium‐ to thick‐bedded dolostone

29

with chert nodules and two black shale layers. The upper shale layer at 50 m marks the lithologic change into the overlying interval of over 30‐m‐thick grey, massive dolostone with black chert nodules in the lower part. The succession is covered upward in the section. Correlation between the northern and southern Xiaofenghe sections is based on the lateral lithologic extension of the limestone interval above the black shale bed that overlies the dolostone succession beneath (Zhu et al. 2013). This correlation level is at 110 m in the northern Xiaofenghe section and at 0 m in the southern Xiaofenghe section (Figs 11, 12). This correlative bed is well recognized in the logs of sections measured by Zhu et al. (2013) but these authors used the unconformity for correlation (at 87 m in the northern Xiaofenghe section A and at 0 m in the southern Xiaofenghe section B). In this study of the southern Xiaofenghe section this erosional surface and unconformity is recognized at – 19 m (Fig. 12). Xiao et al. (2012, fig. 5) have correlated both sections, northern and southern, but not observed the black shale interval (equivalent to member IV) in the southern Xiaofenghe section, in contrast to what was previously described (Yin, L. et al. 2007b; Zhu et al. 2007b; McFadden et al. 2009). These authors agreed that the absence of the black shale interval results from the facies change in a regional scale as it has been suggested by Zhou et al. (2017a) and Jiang et al. (2011). We interpret this missing characteristic sediment interval as showing a stratigraphic gap embracing the depositional time of member IV as in other sections (see below). In the former micropalaeontological studies of the southern section, numerous species were reported but without taxonomic descriptions and documentation, and the Doushantuo Formation was not divided into members (Yin, L. et al. 2007b, 2008; McFadden et al. 2008, 2009) that would allow reference to present assemblages. Although taxonomically described in detail, the microfossils obtained from the Xiaofenghe succession by Zhang et al. (1998b) could neither be included in our assemblages because their occurrence has not been referred to precise stratigraphic levels. This succession has been treated as a composite and generalized for the Yangtze Gorges area and the stratigraphic position of microfossils is unknown. The same predicament exists for species described by Yuan et al. (2002). Certain taxa have since been revised taxonomically or abandoned (Xiao et al. 2014a). Previous record of Papillomembrana compta in the Xiaofenghe section is important because of its geographical distribution outside South China (Vidal 1990), but the information on the

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P. Liu & M. Moczydłowska

stratigraphic level has not been provided otherwise than ‘upper Doushantuo Formation chert layer’ (Yuan et al. 2002). The record of P. compta in the Baizhu section, Baokang County, Hubei Province, remains uncertain as it has been referred to the lower assemblage of member II but without stratigraphic position (Yin, C. et al. 2009b). Yin, L. et al. (2007b) have listed 19 species in the Doushantuo Formation in the Xiaofenghe section, which was a composite succession from the northern and southern sections. We correlate this composite succession and the microfossil occurrences in the interval above 150 m with member III, and the lower interval below 110 m with member II (Yin, L. et al. 2007b, fig. 2). Subsequently, Yin, L. et al. (2008) reported two new species Tianzhushania conferta and T. fissura, which have been synonymized with Tianzhushania spinosa by Xiao et al. (2014). McFadden et al. (2009) listed 21 species in the composite Xiaofenghe section from the interval at 20–180 m. Because the species have not been illustrated we can't revise those which are taxonomically invalid or accommodate other species into our list with certainty, although some species are in common with our record. Microfossils from member III in the southern Xiaofenghe section have been studied by Liu et al. (2013) and in detail by Liu et al. (2014b, fig. 4, and shown in the composite Xiaofenghe section), and consisted of 13 genera and 22 species of ornamented acritarchs. Most of them are restricted to member III. We recovered a more diverse microfossil assemblage of 26 species that is combined with the earlier record and listed in Figure 12. In the present study, 17 chert horizons from the member II yielded 15 genera and 23 species (Fig. 12), including 9 new species: Appendisphaera clustera, Cavaspina conica, Cymatiosphaeroides forabilatus, Dicrospinasphaera improcera, Distosphaera? corniculata, Estrella greyae, Knollisphaeridium coniformum, Membranosphaera formosa, Mengeosphaera lunula. Predominantly, the species present in member II are known in a regional distribution in South China. The cosmopolitan species that are known from other four or five palaeocontinent, such as Appendisphaera grandis and A. tenuis, or at least 2 palaeocontinents, such as Tanarium pilosiusculum and Weissiella grandistella, are of a great value for the interregional correlation. In addition, 3 chert horizons in the lowermost part of member III were examined and 2 of them yielded five species (Fig. 12) that are known commonly in member III (Liu et al. 2014b). The presence of A. grandis at the base of member III demonstrates its continuous range through the members II and III,

FOSSILS AND STRATA

whereas the FAD is here recorded for Tanarium varium and Hocosphaeridium scaberfacium.

The Dishuiyan section The Dishuiyan section and Liuhuiwan section (see below) are partially exposed and very thin successions of the Doushantuo Formation in the eastern flank of the Huangling Anticline (Figs 1B, 13, 14). Remarkably, member IV is absent in both sections and the strata of member III underlie directly the Dengying Formation and its lowermost Hamajing Member. These successions demonstrate the presence of a stratigraphic gap that is equivalent to member IV in other sections and the sedimentological paraconformity between the Doushantuo and Dengying formations. These successions are newly studied and microfossils are recovered for the first time. The Dishuiyan section (Fig. 13) is exposed along the hillside near the Dishuiyan waterfall scenic point. The succession is 50 m thick and consists of the uppermost part of member II and member III, as well as the lower Dengying Formation. The uppermost part of member II is composed of black shale interbedded with grey muddy dolostone and some beds contain chert nodules. The lower boundary of member III is marked by an abrupt change in lithology from black shale (member II) into grey, medium‐ to thick‐bedded dolostone with abundant chert nodules and irregular banded chert. This basal ca. 10‐m interval is succeeded by 5 m of dark grey, muddy dolostone with chert nodules and followed by 18 m of light grey, thick‐bedded dolostone with a few chert nodules. At the top of member III, 2 m of medium‐ bedded muddy dolostone occurs and it terminates the Doushantuo Formation in this section. Without a recognizable sedimentary break, this succession is overlain by light grey massive crystallized dolostone of the Dengying Formation. Because the Doushantuo Formation members are recognized as lithostratigraphic units and not only facies, the missing member IV shows paraconformity and hidden hiatus. This interpretation is supported also by a reduced thickness of member III (35 m) in comparison with other more complete sections (Baiguoyuan, Jiulongwan and Chenjiayuanzi) where member IV is present. We studied 3 chert horizons in member II, which appeared to be barren, and 15 in member III. 12 among the latter preserved 20 genera and 30 species of acanthomorphic acritarchs (Fig. 13), including 4 new species: Bacatisphaera sparga, Briareus vasformis, Laminasphaera capillata and Tanarium uniformum.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Most species in the assemblage are commonly occurring and restricted to member III in the Yangtze Gorges area (Liu et al. 2013, 2014b). Species biostratigraphically useful in a global context are Appendisphaera grandis, Cavaspina acuminata, C. basiconica, Tanarium muntense, Variomargosphaeridium litoschum and Weissiella grandistella. Two species, Alicesphaeridium medusoidum and Calyxia xandaros, are known from Australia and Baltica (the East European Platform) and are recorded for the first time in South China making correlation more accurate.

The Liuhuiwan section The Liuhuiwan section (Fig. 14) is exposed on the hillside near the Liuhuiwan village, and the succession is very thin consisting only of 30 m of member III beneath the lowermost Dengying Formation. The succession measured here is referenced to the level 0 m that is at the base of the outcrop (Fig. 14). The rock interval referred to member III consists of a 10 m of dark grey, medium‐bedded muddy dolostone with abundant chert nodules and intercalated with thin layers of black shale, and succeeded by 15 m of grey, medium‐ to thick‐bedded dolostone with chert nodules and chert bands. Overlying this interval is a 5‐m‐thick grey, medium‐bedded muddy dolostone with a few chert nodules at the top of member III. Without any obvious sedimentological break, member III succession is overlain by light grey, massive dolostone of the Dengying Formation. Comparably like in the Dishuiyan section, the black shale of member IV is missing in this section indicative of a stratigraphic hiatus. Microfossils are recovered for the first time in this section and among 12 examined chert horizons 8 contain acritarchs belonging to 14 genera and 19 species (Fig. 14). Most species in the assemblage are characteristic of member III and Mengeosphaera bellula and M. spinula are restricted to this member (Liu et al. 2013, 2014b; Fig. 15). Species with worldwide distribution are numerous, including Alicesphaeridium medusoidum, Appendisphaera grandis, Cavaspina basiconica, Eotylotopalla strobilata, Tanarium tuberosum, T. paucispinosum, Schizofusa zangwenlongii and Variomargosphaeridium litoschum. The carbon isotope profile of the Liuhuiwan section has been studied by Zhu et al. (2013) and logged by choosing the 0 m level at the base of the dolostone succession that is a few metres higher that the 0 m level herein. The succession has been described in a slightly different lithologic terminology and without reference to the overlying Dengying Formation, and we have not distinguished the

31

phosphorite bed in shale reported in the section. Zhu et al. (2013) correlated the Liuhuiwan succession with the middle Doushantuo Formation and its sequence 2 and the interval of the negative carbon isotope anomaly 3 (N3) but without referencing to the stratigraphic position of the formation members. These authors considered the Liuhuiwan section to represent the best record of the facies change from shale to carbonate intervals in the middle of the second sequence that would be within member II, or it could coincide with the boundary between members II and III by comparison with the Baiguoyuan section. However, our understanding based on the occurrence of microfossil assemblage characteristic of the upper Doushantuo assemblage suggests that the succession represents member III, altogether with its position below the Dengying Formation.

Biostratigraphy General comments Considering the sequence of appearances of discrete species and taxonomic turnovers of age‐restricted microbial assemblages that may be useful for biostratigraphy, it is necessary to trace their records in the most continuous vertical rock successions and in those extending laterally in great expanses across various environments. The species most valuable for biostratigraphy should as far as possible be independent of lithofacies. These are the prerequisites for establishing reliable stratigraphic ranges for species which, together with wide palaeogeographic distribution, enhance their potential for interregional correlation. We analysed those sedimentary successions preserving microfossils in order to detect depositional breaks and time gaps that would affect reading of the stratigraphic ranges of species and compromise the recognition of time equivalence between the sections studied (Fig. 2). The estimation of the relative age of microfossils and their ranges in the Doushantuo Formation is strongly dependent on the understanding of vertical discontinuity, the presence of hiati and their duration, and lateral correlation across various depositional settings on the Yangtze Platform. These aspects have not been fully addressed; a general assumption that they were mostly continuous, condensed successions prevailed, which resulted in reading the fragmentary microfossil vertical extent as indicative of their ranges across the entirety of the lithostratigraphic members and defining the assemblage zones attributed to these members. The time interval of ca. 84 Ma encompasses the Doushantuo Formation, which is recorded by a 220‐

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m‐thick succession at the maximum and includes two major regional unconformities (Zhu et al. 2007b, 2013; Jiang et al. 2011; Lu et al. 2012; Xiao et al. 2014a) and additional paraconformities suggested herein (Figs 2, 3). One of the regional unconformities that has been recognized in the Zhangcunping section in the Yangtze Gorges area and in the Weng'an section in Guizhou Province has been estimated by isotopic datings to be bracketed within 614 ± 7.6 Ma and 609 ± 5 Ma (Liu et al. 2009b; Zhou et al. 2017b). The duration of hiatus involved is thus shorter than the approximate time interval of 614–609 Ma (Fig. 3). The concealed stratigraphic hiati at the unconformities within the Doushantuo Formation are mostly of unknown duration and may be substantial (Fig. 2). The sedimentary portions of the Doushantuo Formation preserved between these unconformities and paraconformities represent limited intervals, and these are even shorter for the portions of the succession that preserve microfossils. This is because the recovery of microfossils is bound to taphonomic windows in the chert nodules and phosphorites that occur at intermittent intervals, whereas the sediment intervals devoid of the above have either not been studied or appeared to be barren. Thus, the species ranges on the time scale of the Doushantuo Formation have been broadly estimated, with the exception of a few species whose first appearance datum is at the dated base of the formation (Fig. 15). Other aspects in recognizing species ranges and applying them to biostratigraphy relate to the taxonomic designation of discrete species, the inclusion of synonymous species and their ranges, and the relative abundance of species accepted as either significant or negligible for defining biozones. We no longer pursue a comparison of the relative abundance of species nor attempt to distinguish the dominant species that others have suggested characterize the two zones in the Doushantuo Formation (Liu et al. 2014b). This is because we do not consider the statistical method viable when dealing with a small number of specimens that are dispersed between several stratigraphic levels of their record (generally in the Ediacaran successions). The relative abundance of any species in the Doushantuo Formation is significantly robust to apply the acme zone concept, even in regional biostratigraphy. In the past, as well as in the present study, several new species have been established by observation of a single or a few specimens that occur only in to the Yangtze Gorges area. They are morphologically complex, distinguishable species documenting the events of diversification significant for palaeobiology and biotic evolution studies, and may be further

FOSSILS AND STRATA

recorded. These species, as well as others that are more abundant but only found in regional distribution or as endemic, are not useful for zonation outside South China. We draw a clear distinction between the species and zones applicable for the regional stratigraphy of the Doushantuo Formation, and others with potential for global subdivision that are based on widely distributed taxa (Fig. 15). The first appearance datum (FAD) of some of the latter taxa has been newly recognized in the basal Doushantuo Formation and in older stratigraphical levels than have been previously known. Detailed information on the stratigraphic occurrence of species in successions we have studied (but not including species reported earlier that were not documented to allow taxonomic evaluation and synonymy) is shown in Figures 4–14 and Table 1. The revised stratigraphic ranges of species are shown in Figure 15; certain species have a well‐defined FAD and last appearance datum (LAD).

The Doushantuo Formation biostratigraphy The biostratigraphic subdivision of the Doushantuo Formation has been developed over years of comprehensive study and continually bound to distinguishing two assemblages and biozones in the lower and upper portions of the formation (see recent review and proposals by Liu et al. 2013, 2014a, b; Xiao et al. 2014a; and references there). The lower Tianzhushania spinosa biozone has been thought to be restricted in the stratigraphic range to the lower member II, and the upper Tanarium conoideum–Hocosphaeridium scaberfacium–Hocosphaeridium anozos biozone to the member III succession (Liu et al. 2014b; Xiao et al. 2014a). The unresolved issue in this subdivision has been the relative age of the Weng'an section and its correlation with the Yangtze Gorges sections. The task includes recognizing the stratigraphic ranges of the Tianzhushania–Yinitianzhushania species plexus and the nominal species of the second zone, all co‐ occurring in the Weng'an section units 4A and 4B. The question is whether these species are restricted to the time interval represented by the lower member II succession in the Yangtze Gorges area (Liu et al. 2014b), and consequently if some of them appear earlier than previously assumed, or whether they extend into younger strata represented by the Weng'an section units 4A and 4B and are correlated with the upper Doushantuo Formation and estimated within ca. 580–600 Ma (Xiao et al. 2014a). The maximum age of units 4A and 4B containing the microfossils at issue in the Weng'an section has been recently estimated to post‐date 614 ± 7.6 Ma and possibly be as old as 609 ± 5 Ma by correlating

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

this section with the isotopically dated Zhangcunping section (Liu et al. 2009b; Zhou et al. 2017a, b). Both successions are lithologically comparable, belonging to the Doushantuo Formation sequences 1 and 2, and consist of two phosphorite units separated by the regional erosional unconformity and karstification surface (Zhou et al. 2005, 2017a, b; Liu et al. 2009b). In the Zhangcunping section, the tuffaceous layer at the basal part of the dolostone underlying this unconformity has provided a SHRIMP II zircon age of 614 ± 7.6 Ma (Liu et al. 2009b). The SIMS zircon U‐Pb age of the tuffaceous layer above the phosphorite unit (upper phosphorite) that overlies the regional erosional unconformity is 609 ± 5 Ma (Zhou et al. 2017b). These dates consistently bracket the maximum age of microfossil assemblages recorded in the Weng'an and Zhangcunping sections. As argued by Zhou et al. (2017b), the lithostratigraphic unit containing the microfossils in the Weng'an succession is pre‐Gaskiers (the Gaskiers glaciation at 582 Ma; Ogg et al. 2016) and older than 580 Ma at a maximum age of 609 ± 5 Ma. We will use the approximate age of ca. 610 Ma for the appearance of certain species recorded in these two successions (Fig. 15). The microfossil assemblages under consideration consist of Tianzhushania spinosa, T. polysiphonia, Yinitianzhushania tuberifera and Appendisphaera grandis (previously identified as Meghystrichosphaeridium perfectum), Asterocapsoides sinensis, Bacatisphaera baokangensis, Cavaspina acuminata, C. basiconica, Dicrospinasphaera zhangii, Ericiasphaera rigida, E. spjeldnaesii, Hocosphaeridium anozos, H. scaberfacium, Knollisphaeridium maximum (previously Echinosphaeridium maximum pro parte), Tanarium conoideum, Sinosphaera speciosa and Variomargosphaeridium litoschum (Liu et al. 2009b; Xiao et al. 2014a; Zhou et al. 2017b; Fig. 15). We conclude that units 4A and 4B of the Weng'an succession are coeval to the upper member II of the Doushantuo Formation in the Yangtze Gorges at a maximum time horizon ca. 610 Ma (610–580 Ma; Figs 2, 3, 15). Such correlation is supported by the fact that the phosphorite grains and nodules that preserve microfossils in the Weng'an succession are reworked and winnowed (Xiao et al. 1998; Xiao et al. 2014a; Xiao & Knoll 1999; Muscente et al. 2015), and thus derived from the older substrate; and by the record of Tianzhushania, the taxon known exclusively from member II in the Yangtze Gorges area (Liu et al. 2014b). In any possible correlation with the Weng'an succession, the fact is that these species co‐occur and their ranges overlap (Fig. 15). This and a new record presented herein requires the re‐evaluation of the stratigraphic ranges of the nominal

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species and certain other species previously considered to be age‐diagnostic of the two zones as well as redefinition of the zones. The two previously recognized assemblage zones in the Doushantuo Formation comprised taxa that are mostly regionally distributed in South China and have been defined by species restricted in distribution (Tianzhushania, Yinitianzhushania), and by some others that are not taxonomically recognized on other palaeocontinents (i.e. Hocosphaeridium that is attributed to Tanarium). The present estimation of species ranges and the recognition of the FAD of species distributed worldwide provide a new basis for biozonation that may be applied to global Ediacaran subdivision and correlation. This also prompts the need for re‐evaluation of the four zones of the Ediacaran Complex Acanthomorph‐dominated Palynoflora (ECAP) established above the 580 Ma time horizon in Australia (Grey 2005) because of the present record of some characteristic and nominal for these zones species in much older strata. These are, for example, Appendisphaera tenuis, Multifronsphaeridium pelorium, Schizofusa zangwenlongii, Tanarium paucispinosum and Variomargosphaeridium litoschum, the species which appear in the lowest Doushantuo Formation of the earliest Ediacaran age (Fig. 15). In the stratigraphic range chart of species (Fig. 15), the species with global vs regional distribution are marked for the clarity. Species recorded in member II The earliest recorded microfossils derive from member II and certain just a few metres above its lower boundary. They represent the first radiating microorganisms in the Ediacaran Period. Species appearing in the lower member II succession are numerous (n = 47), including 18 new species, and certain are restricted to this member (n = 24), whereas others extend stratigraphically into the member III (n = 23; Fig. 15). An additional 9 species appear in the upper member II (those recorded in the Weng'an and Zhangcunping sections), and thus, the total number of species appearing in member II in South China is 56. Species restricted to member II (Table 1) comprise predominantly newly described taxa, which at the moment may not be used for biostratigraphy because their full stratigraphic ranges and geographical distribution are unknown. These 17 species indicate the rapid radiation of microbiota and increase substantially taxonomic biodiversity from the very beginning of the Ediacaran Period. They are rare and only three species among them are more abundant (Dicrospinasphaera improcera n.

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sp., Ericiasphaera fibrilla n. sp. and Knollisphaeridium heliacum n. sp.). In the member II assemblage (Fig. 15), only Briareus borealis and species of the Tianzhushania– Yinitianzhushania plexus are restricted to this lithostratigraphic unit in the Yangtze Gorges area. Their application to the interregional correlation is limited because of a narrow palaeogeographic distribution. B. borealis is recorded outside South China only in Svalbard by a single specimen (Knoll 1992) and in uncertain stratigraphical position, and therefore is negligible for stratigraphic correlation. The lowermost appearance of B. borealis is stratigraphically relatively high in member II at 43 m above the Doushantuo Formation base in the Jiulongwan section and at 72 m level in the Chenjiayuanzi section (Figs 6, 7). Both records are at single stratigraphic levels and the species range remains uncertain. Species T. spinosa and T. polysiphonia are distributed on two palaeocontinents, South China and India, whereas Y. tuberifera is exclusively known from South China (see under Palaeontological descriptions for references to species distribution). T. spinosa has been assumed to occur in Svalbard, following synonymy of the species by Zhang et al. (1998b, p. 40). These authors synonymized two poorly preserved specimens of ‘?Trachyhystrichosphaera sp.’ from Svalbard, Scotia Group (by Knoll 1992) with T. spinosa, as well as a single unnamed specimen from northern India, Lesser Himalaya, the Krol Belt (by Tiwari & Knoll 1994). Xiao et al. (2014a) followed these occurrences of T. spinosa outside South China but rejected the identification of ? Tianzhushania sp. from Australia by Grey (2005, pp. 327–329, fig. 252). Two specimens of ‘?Trachyhystrichosphaera sp.’ from Svalbard are uncertain in identification, whereas a single specimen from Australia likely represents Tanarium. The occurrence of Tianzhushania spinosa in India and a new record of T. spinosa and T. polysiphonia in the Infrakrol Formation, Lesser Himalaya, is confirmed by Joshi and Tiwari (2016), and thus, Tianzhushania is distributed across two palaeocontinents, South China and India. The stratigraphic position of T. spinosa by Zhang et al. (1998b, fig. 13:1–4) was referred in general terms to the lower and upper Doushantuo Formation in the Yangtze Gorges area. Xiao et al. (2014) referred the species occurrence in the units 4A and 4B in Weng'an section to the upper Doushantuo Formation, whereas Liu et al. (2013, 2014a, b) exclusively to the member II of the lower Doushantuo Formation in the Yangtze Gorges area. This conflictive range of the species has to be reconciled. The stratigraphic range of all three species, T. spinosa, T. polysiphonia and Y. tuberifera, extends

FOSSILS AND STRATA

through the lower part of the member II in the Yangtze Gorges area (Liu et al. 2013, 2014a, b) and the units 4A and 4B in the Weng'an section (Xiao et al. 2014a) that are now confirmed to be at maximum age of 609 ± 5 Ma (Zhou et al. 2017b). Because we consider the units 4A and 4B of the Weng'an succession as the time equivalent to the upper member II, Tianzhushania and Yinitianzhushania extend through most of the member. Consequently, the ranges of the nominal species of the second biozone from the Yangtze Gorges area, including Tanarium conoideum, Hocosphaeridium anozos and H. scaberfacium, are stratigraphically lowered and this zone is abandoned. The ranges of Dicrospinasphaera zhangii, Ericiasphaera rigida and Sinosphaera speciosa, which are known in member II in the Yangtze Gorges area (Liu et al. 2014b; herein) and also co‐occur in the upper Weng'an section (Xiao et al. 2014a), are extended to the upper member II. These species are regionally distributed in South China. The species Multifronsphaeridium pelorium from the member II assemblage in the Yangtze Gorges area has a wider geographical distribution and wider stratigraphic range that is shown in Australia. In Australia, it is recorded above the Acraman impact ejecta layer that is interpolated between calibration points to ca. 580 Ma and up to the level close to ca. 565 Ma (Grey 2005), and thus likely correlative with member III. After reviewing stratigraphic ranges of species in the assemblage from the member II successions in the Yangtze Gorges area and incorporating the record from the Weng'an section, it appears that species having ranges restricted to this member and distributed outside South China are Tianzhushania spinosa, T. polysiphonia and Briareus borealis. Because of their limited geographical distribution, they could be used for regional zones, or as complementary nominal species – T. spinosa – with those cosmopolitan species (Fig. 16). Concurrent species in members II and III The set of taxa ranging through the successions referred to both members II and III studied here accounts for 32 species both having worldwide geographical distribution and known exclusively in South China, and one newly described species Tanarium capitatum n. sp. The most significant stratigraphically are those widely distributed species and persistently recorded throughout both members, including Appendisphaera grandis, A. tabifica, A. tenuis, Tanarium muntense, T. paucispinosum, T. pilosiusculum, T. tuberosum, Eotylotopalla delicata, Weissiella grandistella, Schizofusa zangwenlongii and Hocosphaeridium anozos.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Fig. 16. Biostratigraphic subdivision of the Doushantuo Formation in South China and newly proposed assemblage zones defined by the FAD of the nominal species. The approximate ages of the zone boundaries are estimated from the isotopic ages of strata containing the nominal species and measured at the levels near these species FAD.

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by 50 species, comprising numerous cosmopolitan species. Thirty‐eight species known exclusively in South China include 6 newly described species and 1 new combination (Fig. 15). The 12 species commonly occurring, i.e. those known from three or at least two palaeocontinents, are Alicesphaeridium medusoidum, Ancorosphaeridium magnum, Appendisphaera anguina, Asseserium diversum, A. fusulentum, Calyxia xandaros, Ceratosphaeridium glaberosum, Eotylotopalla strobilata, Gyalosphaeridium pulchrum, Multifronsphaeridium ramosum, Tanarium pycnacanthum and Variomargosphaeridium floridum. Their ranges are not yet fully established with the exception of T. pycnacanthum. From this pattern of the diversity and stratigraphic distribution it is evident that by the time of accumulation of member III the microbial diversification and expansion along shallow marine environments was global and surpassed the preceding time interval.

As aforementioned, several species recorded in the Weng'an and the Zhangcunping successions (Liu et al. 2009a; Xiao et al. 2014a) have their ranges extended to member II. The cosmopolitan species among them are Cavaspina acuminata, C. basiconica, Knollisphaeridium maximum, Tanarium conoideum and Variomargosphaeridium litoschum (Fig. 15). They provide biostratigraphic links with Australia, Siberia, Baltica and India (Fig. 17). Additional species from the Weng'an and Zhangcunping assemblages, yet which are palaeogeographically restricted, are Asterocapsoides sinensis, Bacatisphaera baokangensis, Ericiasphaera spjeldnaesii and Hocosphaeridium scaberfacium (Fig. 15). The species recorded in both members II and III and characteristic of the Doushantuo Formation but only regionally distributed in South China include Mengeosphaera chadianensis, M. gracilis, Ericiasphaera magna, Distosphaera speciosa and Eotylotopalla dactylos (Fig. 15). Discrete species occur in various portions of members II and III (detail records in figured sections), and are approximately shown by range bars in those members (Fig. 15). The compilation of the ranges and recognition of the FAD and LAD for the cosmopolitan and commonly occurring species that are suitable for biostratigraphy and correlation are provided in the following subchapter (Stratigraphic ranges). Species restricted to member III The microfossil assemblage restricted to member III is the most diverse taxonomically and recorded here

Fig. 17. Palaeogeographic distribution of selected species that are significant for biostratigraphy in a global scale (cosmopolitan species) and for regional subdivision (endemic species). The occurrence of species in various palaeocontinents is compiled from the references cited under their palaeontological descriptions. The occurrence in Laurentia refers to Canada and USA.

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The species useful for interregional correlation and establishing the biozones are Tanarium pycnacanthum and Ceratosphaeridium glaberosum.

Establishing stratigraphic ranges of selected species Stratigraphic ranges of species in the Doushantuo Formation studied here are established by their first appearance datum (FAD) and last appearance datum (LAD) within the Ediacaran succession. Because the Doushantuo Formation in the Yangtze Gorges area is preserved in various stratigraphic extents in studied sections and discrete species are recorded discontinuously or in single layer (‘spot’) occurrences, the species ranges are approximately recognized within members with some exceptions. The precise recognition of FAD is possible for species which appeared in the basal part of the formation and a few or a dozen or so metres above the lower boundary of the formation. Some of these species are cosmopolitan and applicable for global biostratigraphy and others are diagnostic for regional Ediacaran subdivision in South China. The accuracy of species FAD within a few million years post‐dating 635–632 Ma is unprecedented. The LAD of certain species is established in the uppermost part of member III that is broadly constrained by the age of the terminal Doushantuo Formation at 551 Ma which has to be further deduced by a time interval allocated to the deposition of member IV succession (at maximum 20‐m‐thick shale; Fig. 2). The FAD and LAD are estimated for selected species which are the most accurately recorded and which ranges are traced in several sections (Fig. 15). The FAD of some species is however recognized outside the studied Yangtze Gorges area in units 4A and 4B of the Weng'an section and attributed here to the upper member II of the Doushantuo Formation (Fig. 15). Certain cosmopolitan species recorded in South Australia in the time interval of 580–565 Ma (Grey 2005; Willman & Moczydłowska 2008) provide additional information on the recognition of their upper range and below the time horizon at 565 Ma (Fig. 15). The LAD is constrained for species recorded in the terminal Ediacaran of Mongolia (Anderson et al. 2017). Species having ranges restricted to member II (Table 1) and known outside South China are very few (Fig. 15). The FAD of Tianzhushania spinosa and Yinitianzhushania tuberifera is at the level of 6.8 m above the Doushantuo Formation base in member II in the Chenjiayuanzi section (Fig. 7). This is the lowermost occurrence of any species in the formation and in the Ediacaran System globally. The

FOSSILS AND STRATA

age of this stratigraphic level is slightly younger than 635 Ma at the lower boundary of the Doushantuo Formation and close to 633 Ma that are the ages obtained in the in the Jiuqunao section (= Jijiawan section; Condon et al. 2005) and are extrapolated to the correlative and coeval Chenjiayuanzi succession (Fig. 7). T. spinosa occurs in several sections including Jiuqunao, Jiulongwan, Wangfenggang, Niuping, northern and southern Xiaofenghe, and Nantuocun (Yin, L. et al. 2011b; Liu et al. 2013, 2014b; present new record), but is restricted to the intervals within the lower–middle part of member II. The most comprehensive record is in the Niuping section in the interval 20–108 m and the LAD is at the level of 108 m (Liu et al. 2013; Fig. 10). The record of Y. tuberifera is similar in the lower–middle part of member II in the Jiulongwan, Niuping, Wangfenggang, northern and southern Xiaofenghe sections (Liu et al. 2013; new record). The species LAD is at the 112 m level in the northern Xiaofenghe section (Fig. 11). The range of T. polysiphonia is within the lower half of member II and known from the Jiulongwan, Chenjiayuanzi, Wangfenggang, Niuping, northern and southern Xiaofenghe sections (Liu et al. 2014b; new record). The species FAD is 9.5 m above the base of the Doushantuo Formation in the Chenjiayuanzi section and the LAD at 65 m in the Niuping section. The LAD of all three species, as aforementioned, is recognized in the Yangtze Gorges area. However, because they co‐occur in the units 4A and 4B in the Weng'an section (Xiao et al. 2014a), which are correlated here with the upper member II, the upper range of the species may be stratigraphically slightly higher (Fig. 15). The age of the Weng'an record is ca. 614–609 Ma and pre‐dates 580 Ma (Zhou et al. 2017b; Figs 2, 3) and is here further referred to ca. 610 Ma. Cosmopolitan species that are distributed across five to three palaeocontinents and extend through members II and III of the Doushantuo Formation are considered for global biostratigraphy. Some of them are now recorded at their lowermost ever known globally occurrence in the Yangtze Gorges area in member II and include Appendisphaera grandis, A. tabifica, A. tenuis, Tanarium tuberosum and Weissiella grandistella. The range of A. grandis recognized in the Yangtze Gorges area is comprehensive, well documented in several sections by numerous occurrences and specimen abundance, and consistent stratigraphically. Its FAD is established precisely in the Wangfenggang section and is inferred to be at 633 Ma. The species extends in South Australia to the level which age is broadly estimated to precede 565 Ma (Grey 2005). The species LAD is recognized in Mongolia, where

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

it occurs right below the Ediacaran–Cambrian boundary (Anderson et al. 2017). The species lasted several tens millions of years from the beginning of the Ediacaran Period to its terminal age. The species is distributed across 4 palaeocontinents (Fig. 17). The FAD of Appendisphaera grandis is at the stratigraphic level of 9.4 m above the base of the Doushantuo Formation in the lowermost part of member II in the Wangfenggang section (Fig. section). The age of this level is very close to 632.5 ± 0.5 Ma that is the age obtained from the ash bed in the Jijiawan (= Jiuqunao) section at a level of 9.5 m above the base of the Doushantuo Formation (Condon et al. 2005) and both successions – Wangfenggang and Jiuqunao – are directly correlated and coeval in their lowermost portions (Figs 6, 5, respectively). These portions are sedimentologically almost identical and of similar thicknesses. The stratigraphic levels at 9.4 and 9.5 m in the two successions are, in terms of geological time, almost contemporaneous. We extrapolate the age of the FAD of Appendisphaera grandis in the Wangfenggang section to be at about 633 Ma. The species extends in this section through member II and into the lower part of member III up to the level of 142 m and ranges through 134 m of sediment interval. Stratigraphically, the most extensive range of A. grandis is in the Niuping section (Fig. 10) where it spans the interval from 20 m above the base of the Doushantuo Formation up to the topmost member III at 190 m (a 170‐m‐thick succession). In this section, member III is truncated by an unconformity, which involves a hiatus that is equivalent to the depositional time of member IV, placing it below the succeeding Dengying Formation. Similarly, the species range in the Chenjiayuanzi section extends from 12 m above the base of the Doushantuo Formation up to the upper member III at 151 m. This level is just below the unconformity 152 m level (Fig. 7). In the Baiguoyuan section, A. grandis occurs very high stratigraphically in the member III succession at the level that is 23 m below the base of the member IV which coincides with the unconformity. Altogether in the Yangtze Gorges area, the uppermost occurrence of Appendisphaera grandis does not document its upper stratigraphic range because member III succession is truncated by unconformity and the species record is interrupted (and similarly other species in such stratigraphic position). A. grandis occurs in South Australia in the Officer Basin at a depth of 427.00 m in the Giles 1 borehole in the topmost Tanana Formation of the Ungoolya Group and within the Australian ECAP Zone 4 (ECAP is the Ediacaran Complex Acanthomorph‐dominated Palynoflora by Grey 2005; Willman & Moczydłowska

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2008). This occurrence is below the time horizon at 565 Ma (Fig. 15). The stratigraphically highest global range of A. grandis is recorded in northern Mongolia in the upper Khesen Formation that is of the latest Ediacaran age (Anderson et al. 2017). This record documents not only a wider range of the species, and among only a few species known to extend above the Doushantuo Formation correlative strata (Fig. 15), but likely across the entire Ediacaran System. Although not more precisely estimated within the terminal Ediacaran time scale or constrained by isotopic dating, the record in Mongolia seems to be the global LAD of the species. Following the same procedure of recognizing the total range, the FAD of Appendisphaera tabifica is recorded at 48 m above the base of the Doushantuo Formation in the Wangfenggang section that is within the lower member II. The species uppermost occurrence in this section is in the lowermost member III at 142 m; thus, the range extends through a 94‐m‐thick succession. The species total range is not fully recorded here because the section is covered upward. The LAD is known in South Australia at a depth of 425.75 m in the Giles 1 borehole, in the topmost Tanana Formation of the Ungoolya Group (Willman & Moczydłowska 2008) and preceding the time horizon at 565 Ma. Appendisphaera tenuis appears in the Wangfenggang section at the level of 55 m in the middle member II that is currently its FAD, and it extends over 85‐m interval to the lower member III at the level of 140 m (Fig. 9). The species is known additionally at a single level of 134.50 m in member III in the Chenjiayuanzi section. The species upper range is documented in South Australia at a depth of 425.75 m in the Giles 1 borehole, in the topmost Tanana Formation attributed to the ECAP Zone 4 (Willman & Moczydłowska 2008) at the same stratigraphic level as A. tabifica. The LAD may be recognized in Mongolia in the terminal Ediacaran, where the species is recorded in the upper Khesen Formation (Anderson et al. 2017). However, the species is not illustrated and its LAD not yet confirmed or accurately stratigraphically constrained. Tanarium tuberosum FAD is recognized at 30 m in the middle member II in the Jiuqunao section. This FAD level is about 20 m above the ash layer that has been dated to 632.5 ± 0.5 Ma (Condon et al. 2005) and may be estimated to be no younger than 620 Ma (Fig. 5). The species is known also in the Wangfenggang section in the lower member III interval of 138–142 m (Fig. 9). In the southern Xiaofenghe section it is recorded in the lower member III at 58 m and in the Niuping member III at 159 m. The uppermost occurrence in the Liuhuiwan section

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is in the upper member III succession at 14 m below the paraconformity separating the Doushantuo Formation from the Dengying Formation. The boundary between the two formations coincides with the paraconformity and involves hiatus, and thus may not show the entire range of the species. In South Australia, the species LAD is at a depth of 474.75 m in the Giles 1 borehole in the middle Tanana Formation within the ECAP Zone 3 (Willman & Moczydłowska 2008) and well below the time horizon at 565 Ma (Grey 2005). The FAD of Weissiella grandistella is recognized exactly like that of A. grandis at the level of 9.4 m above the base of the Doushantuo Formation in the lowermost member II in the Wangfenggang section (Fig. 9) and estimated to about 633 Ma (see above). The species occurs in this section at several stratigraphic horizons in members II and III and extends through the interval of 134 m up to 142 m, which is in the lower member III. Additional occurrence of the species is in the Jiulongwan section at 35 m above the base of the Doushantuo Formation in the lower member II. The LAD of the species is recognized in the section Chenjiayuanzi at ca. 148 m in the upper member III, and below the unconformity at 152 m (Fig. 7). The species ranges in the southern Xiaofenghe section through the upper member II and lower member III succession (60‐m‐thick interval), and in the Niuping section through most of member III in the interval 160–182 m. The total range is across members II and III of the Doushantuo Formation (Fig. 15). Other species that are less widely distributed but across three or two palaeocontinents and extend across members II and III of the Doushantuo Formation have also good biostratigraphic potential. Tanarium muntense is sparsely recorded and its FAD is at 23 m in the lower member II in the Niuping section. The species extends through most of member III in the Dishuiyan section in the interval 11–22 m, where the member is terminated by an unconformity at 28 m (Fig. 13). In South Australia, the range of T. muntense is narrow within the upper part of the ECAP Zone 1 and above the Acraman impact ejecta layer that is estimated to be ca. 580 Ma (Grey 2005). The record in the Yangtze Gorges area is more comprehensive, extends stratigraphically higher and consequently bears meaning for the re‐ evaluation of the ranges of this and some other species as well as the biozones in South Australia. Tanarium paucispinosum FAD is recorded at the level of 23 m in the lower member II in the Niuping section, and species extends across 23 to 70‐m interval. The LAD is recognized at 150 m in the upper member III in the Chenjiayuanzi section and below

FOSSILS AND STRATA

the unconformity at 152 m that is succeeded by member IV (20‐m‐thick shale). The species extends in this section in the interval 128–150 m (Fig. 7). Additional species occurrences are recorded additionally in the lower member II in the Wangfenggang section (48 m level) and in the middle member III in the Baiguoyuan section. Tanarium pilosiusculum FAD is established at 9.4 m above the base of the Doushantuo Formation in the lowermost member II succession in the Wangfenggang section like Appendisphaera grandis and Weissiella grandistella. The species uppermost appearance in this section is at 138 m in the lowermost member III succession, and the total range embraces a 130‐m‐thick rock interval. In the Niuping section, the species is recorded within the interval of 64–186 m of the upper member II and member III. Its LAD is recognized here at 186 m of the upper member III and much higher stratigraphically than in the Wangfenggang section. This level is shortly below the unconformity/paraconformity that terminates the Doushantuo succession in the Niuping section and embraces a hiatus that is marked by the absence of member IV. The species upper occurrence is also recorded in the middle member III in the Baiguoyuan section at the level of –33 m below the base of the member IV, that is at the level of unconformity separating members III and IV (Fig. 4). The species Eotylotopalla delicata FAD is recorded in the upper member II at 48 m in the Jiuqunao section (Fig. 5). It also occurs at the level of 72 m in the member II of the Chenjiayuanzi section. The species LAD is at the level of 24 m in the member III in the Dishuiyan section and a few metres below the unconformity truncating this member (Fig. 13). The species total range may not be fully recognized because of the ‘spot’ occurrences in the Yangtze Gorges area and additional occurrence on the East European Platform in Baltica (Vorobeva et al. 2009a, b). The FAD of Schizofusa zangwenlongii is recorded in the middle member II at 33 m in the Jiuqunao section. Its LAD is at 151 m in the upper member III in the Chenjiayuanzi section and below an unconformity at 152 m that is succeeded by member IV strata (20‐m‐thick shale) (Fig. 7). The species occurrences are recorded in member III in the Baiguoyuan, Liuhuiwan, southern Xiaofenghe and Dishuiyan sections. In South Australia, the species ranges through the ECAP Zones 2 and 3 that are broadly within the middle time interval of 580–565 Ma (Grey 2005). The present record is thus much earlier and, based on the present correlation, it is below the 580 Ma time horizon (Fig. 15). Variomargosphaeridium litoschum occurs on 2 palaeocontinents and its range in the Yangtze Gorges

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

embraces members II and III in several sections. Herein, it is recorded in the interval of 128–151 m in the Chenjiayuanzi section and in the interval of 5– 22 m in the Dishuiyan section, both referred to member III. The species occurs in member II in the Qinglinkou (level 29.35 m) and Jinguadun (level 64.40 m) sections as single layer occurrences (Ouyang et al. 2015) and in unit 4B of the Weng'an section (Xiao et al. 2014a), which is correlated with this member. The species FAD and LAD have to be better defined but the lowermost stratigraphic position in the member II of the Doushantuo Formation (Fig. 15) shows the earlier range than recorded in South Australia, where the species extends through the ECAP Zones 2 and 3 within the time interval 580–565 Ma (Grey 2005). Several other cosmopolitan species previously known in the Yangtze Gorges area to be restricted in their occurrence to member III of the Doushantuo Formation (Liu et al. 2014b) are now recognized to have earlier appearances, following their record in units 4A and 4B of the Weng'an succession (Xiao et al. 2014a). The occurrence in the Weng'an section provides the FAD for these species, if accepting the proposed correlation. The stratigraphic ranges of three species that have been used to define the Tanarium conoideum– Hocosphaeridium scaberfacium–Hocosphaeridium anozos Assemblage Zone in the upper Doushantuo Formation member III in the Yangtze Gorges area and, in general, applied to South China (Liu et al. 2014b; Xiao et al. 2014a) are revised here because of their new record and also the record in the Weng'an section. Tanarium conoideum is restricted to member III interval in the Yangtze Gorges area but its range is wider in the Weng'an section (Fig. 15). In the Yangtze Gorges area, the species lowermost occurrence is about 3 m above the base of member III in the Wangfenggang section at 138 m. The species occurs also in the lowermost member III at 160 m (and about 12 m above the member basis) in the Niuping section. The uppermost occurrence is in the middle member III level –23 m in the Baiguoyuan section, which is at the same time 23 m below the unconformity separating members III and IV. However, the species FAD is in unit 4A in the Weng'an section following record by Xiao et al. (2014a). The species LAD is recognized in South Australia at a depth of 425.75 m in the Giles 1 borehole in the topmost Tanana Formation, and attributed to the ECAP Zone 4 (Willman & Moczydłowska 2008). The species range recognized in South Australia is much wider and extends into the higher stratigraphic level and close to the time horizon at 565 Ma (Grey 2005) and the species is widely distributed on four palaeocontinents.

39

The record of Hocosphaeridium anozos reported here from member II excludes the species from being diagnostic of the upper assemblage zone of the Yangtze Gorges area. Its FAD is at 23 m in the lower member II in the Niuping section and the species ranges to the level of 191 m in the upper member III and below the unconformity terminating the Doushantuo Formation in this section. The total range in the Niuping section is through a 168‐m‐ thick interval (Fig. 10) and spans most of the Doushantuo Formation succession that is at maximum 220 m thick in the Yangtze Gorges area. New but fragmentary record is from the Dishuiyan section in the lower member III succession which is less than 30 m thick and limited by the unconformity (Fig. 13). The species LAD (as attributed to the senior synonym Tanarium anozos) is recognized in South Australia at a depth of 425.75 m in the Giles 1 borehole in the topmost Tanana Formation and attributed to the ECAP Zone 4 (Willman & Moczydłowska 2008). In South Australia, the species range is higher stratigraphically and close to the time horizon at 565 Ma (Grey 2005). The range of Hocosphaeridium scaberfacium is identical to that of Tanarium conoideum. In the Yangtze Gorges area, the species is recorded in member III as it had been known hitherto (Liu et al. 2014b), and its lowermost occurrence is exactly at the base of the member III, which is 35 m in the southern Xiaofenghe section (Fig. 12). The species occurs approximately 3 m above the base of member III in the Wangfenggang section at 138 m. The species record in the Weng'an section (Xiao et al. 2014a) is presently attributed to the upper member II and thus earlier and showing its FAD (Fig. 15). The species LAD is at 191 m in the upper member III in the Niuping section (Fig. 10), although the range may not be fully recognized because of the unconformity in this section and stratigraphic hiatus equivalent to the missing member IV (Fig. 10). Furthermore, the occurrence of the following cosmopolitan species in the Weng'an section provides the FAD for these species within member II and extends their total ranges. Cavaspina acuminata is distributed on five palaeocontinents but in the Yangtze Gorges area it sparsely occurs within the member III succession. The lowermost occurrence is at 12 m above the base of the member in the Dishuiyan section (one layer). The other record is at 54 m in the lower part of the member in the southern Xiaofenghe section (one layer). The FAD is recognized in the Weng'an section in unit 4B (Xiao et al. 2014a) (Fig. 15). The species LAD is recorded in South Australia at a depth of 427.00 m in the Giles 1 borehole in the topmost Tanana Formation and

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attributed to the ECAP Zone 4 (Willman & Moczydłowska 2008) and below the time horizon at 565 Ma (Grey 2005). Similarly, Cavaspina basiconica is known from four palaeocontinents, and its lowermost occurrence in the Yangtze Gorges is at 5 m above the base of member III in the Dishuiyan section. The species uppermost occurrence is at the level of 188 m in the uppermost member III in the Niuping section, but in this section the terminal part of the succession is not known because of an unconformity/paraconformity at 192 m and the absence of the member IV of the Doushantuo Formation (Fig. 10). The species FAD is in unit 4A of the Weng'an section (Fig. 15). The species record in the Hunan Province in the Lujiayuanzi section at the level of 40 m above the base of the Doushantuo Formation (Ouyang et al. 2017) and presumable in member II supports the lower range extension. The species upper range is recorded in South Australia, at a depth of 425.75 m in the Giles 1 borehole, in the topmost Tanana Formation attributed to the ECAP Zone 4 (Willman & Moczydłowska 2008). The record of C.? basiconica in the upper Khesen Formation in Mongolia and estimated to be of the latest Ediacaran age (Anderson et al. 2017) may be the potential LAD of the species. However, the specimens preserved by phosphatization are identified with uncertainty and the species awaits to be confirmed as to its topmost Ediacaran occurrence. Knollisphaeridium maximum is distributed worldwide on five palaeocontinents and in the Yangtze Gorges its lowermost occurrence is at the very base of member III (0.35 m level) in the Dishuiyan section, where it extends to the level of 22.50 m. Member III succession is terminated at 28 m by an unconformity below the Dengying Formation. In the Liuhuiwan section, the species upper range in member III is similar and also shortly below an unconformity between member III and the Dengying Formation. The species ranges through relatively narrow intervals of member III in the Baiguoyuan and Liuhuiwan sections, but most of member III in the Niuping and Chenjiayuanzi sections. The species FAD is in unit 4A of the Weng'an section and its LAD is currently recognized at 151 m in the Chenjiayuanzi section, where it extends between ca. 128– 151 m and just below an unconformity at 152 m (Figs 7, 15). The only species that seem to have well‐recognized ranges and restricted stratigraphically to member III in the Yangtze Gorges area, and known from two palaeocontinents, are Tanarium pycnacanthum and Variomargosphaeridium floridum (Fig. 15). The FAD of Tanarium pycnacanthum is about 3 m above the base of the member III in the Wangfenggang

FOSSILS AND STRATA

section at 138 m (Fig. 9), and the species ranges through member III interval at 160–178 m in the Niuping section. The LAD is recognized in South Australia at a depth of 427.00 m in the Giles 1 borehole in the topmost Tanana Formation in the ECAP Zone 4 (Willman & Moczydłowska 2008) and below 565 Ma horizon. The record of Variomargosphaeridium floridum is sparse in the lower–middle member III and not significant stratigraphically. The species occurs at the base of member III at 139 m and 142 m in the Wangfenggang section, in the lower member III at 0.6 m, 11.5 m and 12.0 m in the Dishuiyan section, and in the middle member III at 54 and 55 m in the Southern Xiaofenghe section (Figs 9, 13, 12, respectively). Following the here established ranges of cosmopolitan and characteristic species and selecting the species, which have well‐defined FAD and show the sequence of appearances in the geologic succession of the Doushantuo Formation, we propose the new zones for the Yangtze Gorges area in South China.

New biozones in the Doushantuo Formation The assemblage zone is the type of biozone that is defined on the basis of the vertical ranges of a number of fossil taxa. These taxa may represent various modes of life (benthic, planktonic, nektonic) of fossils in the assemblage (Doyle et al. 1994) or may include taxa having partial range or consecutive ranges, or concurrent ranges within the assemblage zone in the lack of a single taxon useful for recognizing total range zone (recognized under the rules of the ISSC; McGowran 2005). The proposed assemblage zones are defined by their lower boundaries at the FAD of selected nominal species, which, although having relatively long total ranges, appear in a stepwise succession throughout the Doushantuo Formation and delimit corresponding rock intervals (zones) and time intervals (biochrons). There are presently no short‐ranging cosmopolitan species known in the Doushantuo Formation; some potential species have ranges that are not yet precisely recognized but if they were would be suitable for establishing the taxon range zones. The assemblage zones are characterized by several concurrent species within the zone range delimited by the FAD of the nominal species of one zone and those of the succeeding zone. The assemblage zones proposed here combine the concurrent ranges zone and interval zone of successive taxa and include barren zone (Fig. 16) and are in accord with the concept of this type of zone recognized by the rules of the ICS International Stratigraphic Guide Hedberg 1976 (Doyle et al. 1994; McGowran 2005).

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Based on the present and revised record of microfossils and recognition of species FAD and LAD, we have selected the cosmopolitan species and some regional that are characteristic of the Doushantuo Formation to define the Ediacaran zones (Fig. 16). These are, in ascending order: Appendisphaera grandis–Weissiella grandistella–Tianzhushania spinosa, Tanarium tuberosum–Schizofusa zangwenlongii, Tanarium conoideum–Cavaspina basiconica and Tanarium pycnacanthum–Ceratosphaeridium glaberosum Assemblage Zone. The estimated duration of the proposed zones (i.e. biochrons) is ca. 13, 10, 30 and 15 Ma, respectively, for the succeeding zones. Because of the discontinuity of rock successions and fossiliferous intervals, these time intervals are not proportional to the thicknesses of particular zones. The duration of Ediacaran biochrons and their time resolution is comparable to those recognized in the Cambrian and younger periods on the basis of microfossils and animal fossil taxa (Moczydłowska 1998; Grey 2005). Appendisphaera grandis–Weissiella grandistella– Tianzhushania spinosa Assemblage Zone Definition. – The lower boundary of the zone is at the FAD of Appendisphaera grandis, Weissiella grandistella and Tianzhushania spinosa that are nominal species. The upper boundary is defined by the FAD of T. tuberosum, i.e. the nominal species of the overlying zone. Reference section. – The Wangfenggang section, Yangtze Gorges area, South China. Reference horizon. – The lower boundary is in the Doushantuo Formation, the lowest part of member II at the level of 9.4 m in the Wangfenggang succession (Fig. 9). Remarks. – The co‐occurrence of all three nominal species and the FAD of cosmopolitan A. grandis and W. grandistella are recorded in the reference section. The FAD of T. spinosa that is the characteristic regional species lies in the lowest part of member II in the Chenjiayuanzi section at the level of 6.8 m (Fig. 7). The Wangfenggang and Chenjiayuanzi successions are correlative sedimentologically and stratigraphically in their basal portions (member I and II) and the levels of FAD of all three species are contemporaneous and estimated at ca. 633 Ma time horizon (Figs 15, 16).

41

Tanarium tuberosum–Schizofusa zangwenlongii Assemblage Zone Definition. – The lower boundary is marked by the FAD of T. tuberosum. The upper boundary is defined by the FAD of T. conoideum and Cavaspina basiconica that are the nominal species of the overlying zone. Reference section. – The Jiuqunao section, Yangtze Gorges area, South China. Reference horizon. – The lower boundary is in the Doushantuo Formation, the lower part of member II at the level of 30 m in the Jiuqunao succession (Fig. 5). Remarks. – The FAD of S. zangwenlongii that is the other nominal species of the zone is slightly higher than this of T. tuberosum in the Jiuqunao succession at the level of 33 m. The lower boundary of the zone is estimated at ca. 620 Ma time horizon. Tanarium conoideum–Cavaspina basiconica Assemblage Zone Definition. – The lower boundary of the zone is at the FAD of both nominal species. The upper boundary is not yet defined and co‐occurs within the topmost part of member II of the Doushantuo Formation. Reference section. – The Weng’an section, the Guizhou Province, South China. Reference horizon. – The lower boundary is in Doushantuo Formation, the upper part of member II at the base of unit 4A of the Weng’an succession (see section in Xiao et al. 2014a). Remarks. – The lower boundary is constrained by a time horizon at ca. 610 Ma and considered to be within the upper member II. The nominal species are cosmopolitan in distribution. Tanarium pycnacanthum–Ceratosphaeridium glaberosum Assemblage Zone Definition. – The lower boundary of the zone is at the FAD of both nominal species. The upper boundary is not yet defined because the sedimentary succession of the Doushantuo member III is truncated by unconformity. Reference section. – The Wangfenggang section, Yangtze Gorges area, South China.

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FOSSILS AND STRATA

Reference horizon. – The lower boundary is in the Doushantuo Formation, the lowest part of member III at the level of 138 m, that is, 3 m above the member III base in the Wangfenggang succession (Fig. 9). Remarks. – The zone may extend through the entire member III and may span the time interval estimated to ca. 580–565 Ma. The time horizon of ca. 580 Ma is shortly after the Gaskiers glaciation age (582 Ma) and the corresponding glacio‐eustatic sea level fall expressed by the regional unconformity between members II and III in South China (Xiao et al. 2014a; Zhou et al. 2017a). The upper boundary is estimated at the time horizon of both species uppermost occurrence in Australia.

Conclusions In the present investigation of eleven exposed successions of the Doushantuo Formation located in the vicinity of the Huangling Anticline in the Yangtze Gorges area, we document the occurrence of diverse organic‐walled microfossils entombed in chert nodules. Microfossils are well‐preserved and taxonomically diagnostic. They are useful for biostratigraphy on both a regional and global scale for the Ediacaran System. The results are summarized as follows:

•

•

•

•

• The microfossils studied by transmitted and polarized light microscope and illustrated here include over one hundred species (n = 107), among which 24 are newly described. Microfossil taxonomy has been revised, several species diagnoses emended, some synonymized, and three new combinations are proposed. • The stratigraphic ranges of the species recorded here are evaluated based on new records and the correlation of strata containing them, resulting in the recognition of the FAD and LAD of numerous species that are both cosmopolitan and regional in distribution, and relevant for biostratigraphy. • The geological succession of the Doushantuo Formation is critically reviewed from the point of view of its sedimentological and depositional development. Particular attention has been paid to regional unconformities and stratigraphic hiati and we recognize additional un- and paraconformities within the formation. • The Doushantuo Formation is sedimentologically discontinuous, highly condensed in parts (phosphorites), and disrupted by stratigraphic hiati of unknown duration at the un- and paraconformities levels. Because of these conditions, the relative

•

thicknesses and ratio of sedimentation of particular successions are unreliable as sources for the estimation of time intervals involved in their deposition, with the exception of those few intervals with isotopic datings in the lower part of the formation that are attributed to member II. The incompleteness of the Doushantuo Formation is also clearly demonstrated by its total maximum thickness of ca. 220 m within the time span of ca. 84 Ma that is based on the isotopic ages of its lower and upper boundaries at 635 and ca. 551 Ma, respectively. For comparison, the terminal Ediacaran Dengying/Liuchapo formations, with a maximum thickness of 1000 m for the Dengying Formation, were deposited within ca. 10 Ma (551–541 Ma) and consist of dolostone, as does most of the Doushantuo Formation. Understanding the Doushantuo Formation's depositional, relative stratigraphic and isotopic age relationships is vital for establishing reliable species ranges and biozones. Species ranges are often recognized in part because of biased records (limited to chert nodules intervals). However, we have recorded numerous species at their lowest ever globally recorded stratigraphic positions in the basal Doushantuo Formation and in geological intervals isotopically dated within the Ediacaran System. Species with well-recognized FAD are used for defining the following assemblage zones, in ascending order: Appendisphaera grandis–Weissiella grandistella–Tianzhushania spinosa, Tanarium tuberosum–Schizofusa zangwenlongii, Tanarium conoideum–Cavaspina basiconica and Tanarium pycnacanthum–Ceratosphaeridium glaberosum Assemblage Zone. The lower boundaries of the zones are estimated to occur at ca. 633, 620, 610 and shortly after 580 Ma horizons by interpolation of the isotopically dated horizons within the successions (633 and 610 Ma), and by inference of the glacio-eustatic sea level fall at 580 Ma Gaskiers glaciation that caused the regional unconformity in the Doushantuo Formation between members II and III. The uppermost Doushantuo Formation has not yet yielded such microfossils as are dealt with in this study, and therefore, no zone has been established. The earliest Ediacaran evolutionary event globally is the microbial and allegedly holo- or metazoan radiation. Many species originate at ca. 633 Ma, shortly after the end of the Marinoan glaciation. It prompts questions as to the biological affinities of recorded microfossils that are conceived as algal cysts in majority and some other among protists in general terms, or those of

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Tianzhushania plexus as putative diapause egg cysts and embryos.

Systematic palaeontology Remarks. – The microfossil taxa are described alphabetically because their natural systematics are not yet resolved with certainty although some taxa are recognized as possible green microalgae, whereas individual species are among putative metazoan egg cysts. All microfossils are eukaryotic and some taxa are attributed to the protistan group of Chloroplastida and division Chlorophyta (according to the classification by Adl et al. 2012) based mostly on comparative morphology and phenetic features, but also on cell‐wall ultrastructure and biochemical properties (although less available). The chlorophyte algal affinities are inferred for example for Ancorosphaeridium, Appendisphaera, Multifronsphaeridium and Tanarium (Moczydłowska 2005, 2015; Moczydłowska & Nagovitsin 2012). The genus Tianzhushania is inferred to be a putative metazoan cyst or embryo (Yin et al. 2004; Yin et al. 2007b) or a holozoan reproductive cyst (Huldtgren et al. 2011; but see Cunningham et al. 2017). The microfossil taxonomy is informal because phylogenetic affiliations are largely unknown and the form‐genus and form‐species are recognized according to the rules of International Code of Nomenclature for algae, fungi and plants (Melbourne Code 2011). The species synonymy is simplified and includes citations of illustrated specimens (not all published occurrences) and relevant to establishing their stratigraphic ranges and palaeogeographic distribution. The identification and morphological terminology follow the conventional application of terms in biological and palaeontological descriptions of protoctists (Moczydłowska et al. 1993; Grey 2005; Moczydłowska 2005; Liu et al. 2014b; Xiao et al. 2014a). Our observations are based on comparative studies of the Ediacaran microfossil collections and those of other ages from China, Australia, Siberia and Baltica, and both preserved by diagenetic permineralization by opaline silica and phosphate and those organically preserved in fine‐grained siliciclastic sediments. The taphonomic variations related to preservation modes are better understood and their influence on the species identification is reduced. The species occurrence in the Doushantuo Formation is listed additionally in Table 1 and their palaeogeographic distribution in Figure 17.

43

Repository. – Type and figured specimens are curated in the palaeontological collections of the Institute of Geology, Chinese Academy of Geological Sciences, Beijing. The illustrated microfossils are contained in thin sections and carry the pre‐fix IGCAGS, followed by the number of the thin section, and specimen position by microscope coordinates and England Finder. Genus Alicesphaeridium Zang in Zang & Walter, 1992, emend. Grey, 2005 Type species. – Alicesphaeridium medusoidum Zang in Zang & Walter, 1992, emend. Grey, 2005; from central Australia, the Amadeus Basin, Pertatataka Formation, Rodinga 4 borehole at a depth of 53.86–54.14 m, Ediacaran (Zang & Walter 1992b). Other species. – We consider the genus being monospecific and other species, such as A. cornigerum Vorobeva, Sergeev & Knoll, 2009, A. lappaceoum Vorobeva, Sergeev & Knoll, 2009, and A. tubulatum Vorobeva, Sergeev & Knoll, 2009 (Vorobeva et al. 2009a), are synonymous to the type species. Alicesphaeridium medusoidum Zang in Zang & Walter, 1992, emend. Grey, 2005 Figure 18 1992 Alicesphaeridium medusoidum gen. et sp. nov.; Zang in Zang & Walter 1992b, pp. 24, 26, figs 13, 14A–G, 16A–G. 1992 Amadeusphaeridium prodigiosum gen. et sp. nov.; Zang in Zang & Walter 1992b, pp. 26, 29, fig. 19G–J. pro parte 1992 Trachyhystrichosphaera? anelpa sp. nov.; Zang in Zang & Walter 1992b, pp. 110, 112, fig. 82E. non 1992 Trachyhystrichosphaera? anelpa sp. nov.; Zang in Zang & Walter, 1992b, pp. 110, 112, fig. 82A–D, F. pro parte 1992 Filisphaeridium nassokarum sp. nov.; Zang in Zang & Walter 1992b, pp. 42, 46, fig. 39E–G. 1992 Gyalosphaeridium inconstanum sp. nov.; Zang in Zang & Walter 1992b, pp. 54, 58, fig. 41A–I.

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FOSSILS AND STRATA

Fig. 18. Microfossils from the Doushantuo Formation. A–D, Alicesphaeridium medusoidum Zang in Zang & Walter, 1992, emend. Grey, 2005. A, IGCAGS‐CJ537, thin section CJ151.8‐11 (N37, Z: 95 × 14). B, IGCAGS‐DSY072A, thin section DSY8‐18 (P42, Z: 100 × 12). C– D, IGCAGS‐LHW007, thin section LHW‐0.65‐5 (C52/3, Z: 109.5 × 23.2), specimen shown at different focal levels. All microfossil images in this and following figures 19–92 are transmitted light micrographs. For each illustrated specimen in this and following figures, the reference to museum collection number with the acronym IGCAGS, thin‐section number and microscope coordinates (in parentheses, Z = Zeiss Imager A microscope; N=Nikon 80i microscope) are provided.

pro parte 1992 Polyhedrosphaeridium echinatum gen et sp. nov.; Zang in Zang & Walter 1992b, p. 90, fig. 68A–F. non 1992 Polyhedrosphaeridium echinatum gen et sp. nov.; Zang in Zang & Walter 1992b, p. 90, fig. 68G. 2005 Alicesphaeridium medusoidum Zang in Zang & Walter, 1992a; emend.; Grey, pp. 197–200, figs 76A– F, 77A–D. 2006 Cavaspina sp.; Veis, Vorobeva & Golubkova, pl. I, fig. 7, pl. II, figs 3, 5.

2006 ‘Unnamed form 2’; Veis, Vorobeva & Golubkova, pl. fig. 4, pl. II, fig. 2. 2006 ‘Unnamed form 3’; Veis, Vorobeva & Golubkova, pl. I, fig. 3. 2006 Polychedrosphaeridium echinatum Zang et Walter, 1992; Veis, Vorobeva & Golubkova, pl. I, figs 1, 2 (sic; misspelled generic name). 2006 Alicesphaeridium medusoideum Zang et Walter, 1992; Vorobeva, Sergeev & Semikhatov, fig. 2n, q, t, v, x (sic; misspelled species name).

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

2007 Alicesphaeridium medusoideum Zang in Zang & Walter, 1992; Vorobeva, Sergeev & Knoll, pl. 1, fig. K (sic; misspelled species name). 2008 Alicesphaeridium medusoidum Zang, 1992, emend. Grey, 2005; Willman & Moczydłowska, pp. 512, 519, fig. 6A–B. 2009 Alicesphaeridium medusoideum Zang, 1992, emend. Grey, 2005; Vorobeva, Sergeev & Knoll, 2009a, p. 174, fig. 5.1–5.6 (sic; misspelled species name). 2009 Alicesphaeridium cornigerum new species; Vorobeva, Sergeev & Knoll, 2009a, p. 174, fig. 5.7–5.11. 2009 Alicesphaeridium tubulatum new species; Vorobeva, Sergeev & Knoll, 2009a, pp. 174, 175, fig. 6.1–6.3, 6.6. 2009 Alicesphaeridium lappaceoum new species; Vorobeva, Sergeev & Knoll, 2009a, p. 175, fig. 6.4–6.5, 6.7–6.9. 2009 Alicesphaeridium medusoideum; Vorobeva, Sergeev & Knoll, 2009b, fig. 4a (sic; misspelled species name). 2009 Alicesphaeridium spp.; Vorobeva, Sergeev & Knoll, 2009b, fig. 4b, c. Description. – Vesicle circular to oval in outline, originally spheroidal, bearing heteromorphic and unevenly distributed processes. Vesicle surface psilate. Processes are single conical with varying width at the base, more tubular with round or truncate terminations, or wide tubular at the base and terminally divided into conical branches. Processes are hollow inside and freely communicate with the vesicle cavity, and their tips are tapered or dichotomized. Dimensions. – Vesicle diameter 62–244 μm; process length 10–30 μm; width of process bases 7–29 μm (n = 4). Material. – Four relatively well‐preserved specimens. Remarks. – Specimens observed in thin sections show the process distribution only on the vesicle outline. Although unevenly distributed, the processes occur on each part of the vesicle section and clearly

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demonstrate in such view a free communication with the vesicle cavity. Processes are constituted by the vesicle wall extensions. Limited observations by comparison with the specimens extracted from the host sediment and three‐dimensionally preserved do not allow a full appreciation of the original hemispheroidal shape of the vesicle, which was diagnosed for the genus (Zang & Walter 1992b; Grey 2005). The vesicle shape of Alicesphaeridium specimens studied in palynological slides from the Baltica palaeocontinent has been recognized as spheroidal and bearing processes distributed over the entire vesicle surface (Vorobeva et al. 2009a). The latter feature differs from the previously described processes being predominantly confined to the equatorial margin of the vesicle in the type species A. medusoidum (Grey 2005; Willman & Moczydłowska 2008). Process terminations are closed and those described as being open in addition to closed (Zang & Walter 1992b; Grey 2005) are taphonomic artefacts as it has been considered by Vorobeva et al. (2009a). Based on the observations of specimens preserved in various burial conditions (organically preserved specimens and diagenetically permineralized) and taphonomic states, we assume that Alicesphaeridium has a spheroidal vesicle, highly heteromorphic simple and branching processes, which are hollow but closed terminally. They are distributed over the vesicle surface although with various density and distances between one another. Despite a substantial variability of process morphology in a single specimen (heteromorphy) and between recognized four species, we assume that all these species may be conspecific with the type species. Willman & Moczydłowska (2008) contended that the heteromorphy of processes seen in a number of species described informally or as synonymous species is accommodated within the monospecific Alicesphaeridium. The morphologic differentiation ascribed to species A. cornigerum, A. tubulatum and A. lappaceoum, and in distinction from A. medusoidum (Vorobeva et al. 2009a), deals with the abundance of processes and their relative size. The general body plan and shape of processes are similar in all species. A. lappaceoum is unrecognizable from A. medusoidum, or A. cornigerum from A. tubulatum, and they may differ only by minor fluctuations in the proportions of process length to vesicle diameter. The size ranges of vesicle diameter and process length among four species are overlapping or identical (Grey 2005; Willman & Moczydłowska 2008; Vorobeva et al. 2009a). Viewed as infraspecific variants, we support the alternative placement of all species in A. medusoidum as it has been discussed by Vorobeva et al. (2009a).

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Present record. – South China, Hubei Province, Yangtze Gorges area, Chenjiayuanzi, Dishuiyan and Liuhuiwan sections, Doushantuo Formation, member III.

2012 Ancorosphaeridium magnum Sergeev, Knoll & Vorobeva, 2011, emended; Moczydłowska & Nagovitsin, p. 8, fig. 2A–U.

Occurrence and stratigraphic range. – Australia, Amadeus Basin, Rodinga 4 borehole, at a depth of 23.02–58.55 m, Pertatataka Formation; Officer Basin, Munta 1 borehole, at a depth of 1198.6–1736.8 m, and Observatory Hill 1 borehole, at a depth of 264.3 and 233.0 m, lower Ungoolya Group, Ediacaran (Grey 2005). Russia, East European Platform (EEP), Keltminskaya 1 borehole, upper Vychegda Formation, at a depth of 2605–2649 m, Vendian=Ediacaran (Vorobeva et al. 2009a).

Material. – A single specimen with well‐preserved process terminations.

Genus Ancorosphaeridium Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015 Type species. – Ancorosphaeridium magnum Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015; from East Siberia, Patom Uplift, section of the Ura River, Ura Formation, lower Ediacaran (Moczydłowska & Nagovitsin 2012; Moczydłowska 2015). Other species. – A. minor Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012; A. robustum Nagovitsin & Moczydłowska, 2012. Ancorosphaeridium magnum Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015 Figure 19 2008 ‘Envelope having transparent processes with hook-like ends’; Vorobeva, Sergeev & Chumakov, fig. 2d, e. non 2008 ‘Envelope with processes of different shapes within one specimen’; Vorobeva, Sergeev & Chumakov, fig. 2m–o (transferred to A. robustum). 2011 Ancorosphaeridium magnum n. sp.; Sergeev, Knoll & Vorobeva, p. 1001, fig. 4:1–3. non 2011 Ancorosphaeridium magnum n. sp.; Sergeev, Knoll & Vorobeva, p. 1001, fig. 7.1a, b (transferred to A. robustum).

2015 Ancorosphaeridium magnum Sergeev et al. 2011, emended Moczydłowska & Nagovitsin, 2012, emended; Moczydłowska, p. 6, pl. 1, figs 1–4.

Description. – Vesicle circular to oval in outline, originally spheroidal, bearing cylindrical narrow in width processes, which are evenly distributed on the vesicle surface. Processes have small conical bases and slightly widened proximal portions that are terminated by anchor‐shaped tips with a small number of ray elements. Rays are bent towards process stem. Processes are hollow inside up to the end of the rays and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 248 × 310 μm; processes length 74 μm; process basal width 5 μm and stem portion width 2 μm; terminal ray length 10 μm. Remarks. – A single specimen seen in cross section is identified confidently because of the diagnostic anchor‐like tips and long, slender processes, which are known only in this species of Ancorosphaeridium. The conical bases are more prominent than in the organically preserved specimens occurring in siliciclastic sediments (Sergeev et al. 2011; Moczydłowska & Nagovitsin 2012). This may be caused by fluid silica penetrating the sediment during early diagenesis that inflated the process bases from the void of the vesicle cavity. The phenomenon of inflated process bases observed in many Ediacaran taxa, which are preserved by silicification and phosphatization in the Doushantuo Formation, may be a taphonomic feature induced by precipitating mineral solutions. The anchor‐shaped tips of processes are known also in the early Devonian–early Carboniferous microfossil genus Craterisphaeridium from the Toca da Moura Complex of South Portugal (Lopes et al. 2013). Craterisphaeridium Deunff, 1981 has a spheroidal vesicle and long processes. The interior of these processes is freely connected with the vesicle cavity. The processes taper gradually from a wide conical proximal portion and in this shape they differ from cylindrical processes in Ancorosphaeridium. However, the body plan and the unique shape of process tips are similar in both genera. If not being separated by ca. 180 Ma time gap in stratigraphic ranges, they

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 19. A–E, Ancorosphaeridium magnum Sergeev, Knoll & Vorobeva, 2011, emend. Moczydłowska & Nagovitsin, 2012, emend. Moczydłowska, 2015; IGCAGS‐BGY030, thin section BGY5‐2 (Q20/1, Z: 78.5 × 11.1). Arrows in A indicate enlarged fragments shown in B, C and E, respectively. D is enlarged fragment of B.

would be considered as pertaining to a single genus and possible closely related. Present record. – South China, Hubei Province, Yangtze Gorges area, Baiguoyuan section at the level of –29 m, Doushantuo Formation, member III. Occurrence and stratigraphic range. – Russia, East Siberia, Patom Uplift, Ura River section, Ura Formation, Lower Vendian (Vorobeva et al. 2008), lower– middle Ediacaran (Sergeev et al. 2011) or lower Ediacaran (Moczydłowska & Nagovitsin 2012).

A. clustera n. sp.; A. fragilis Moczydłowska, Vidal and Rudavskaya, 1993; A.? hemisphaerica Liu, Xiao, Yin, Chen, Zhou and Li, 2014; A. lemniscata n. sp.; A. longispina Liu, Xiao, Yin, Chen, Zhou and Li, 2014; A. longitubulare Liu, Xiao, Yin, Chen, Zhou and Li, 2014, n. comb.; A. setosa Liu, Xiao, Yin, Chen, Zhou and Li, 2014; A. tabifica Moczydłowska, Vidal and Rudavskaya, 1993, emend.; A. tenuis Moczydłowska, Vidal and Rudavskaya, 1993. Appendisphaera clustera n. sp. Figure 20

Genus Appendisphaera Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005 Type species. – Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Yakutia, Siberian Platform, Zapad 742 borehole, Khamaka Formation, Ediacaran (Moczydłowska 2005). Other species. – A. anguina Grey, 2005; A.? brevispina Liu, Xiao, Yin, Chen, Zhou and Li, 2014; A. clava Liu, Xiao, Yin, Chen, Zhou and Li, 2014;

Holotype. – Specimen IGCAGS‐D2XFH635, thin section XFH0946‐1‐170, D42; illustrated in Figures 20A–C. Paratype, specimen IGCAGS‐ D2XFH329, thin section XFH0946‐1‐43, W21; illustrated in Figures 2D–E. Derivation of name. – From Latin cluster – cluster; referring to the congregation of processes in bunches. Locus typicus. – Yangtze Gorges area, northern Xiaofenghe section.

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Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II, at a level of 105 m. Material. – Six well‐preserved specimens. Diagnosis. – Vesicle large in size, circular in outline, originally spheroidal, bearing cylindrical slender processes clustered in groups of 2–4 processes, and occasionally being single, which are evenly distributed on the vesicle wall. Processes are homomorphic and regular in the shape of thin cylinders that are sharp‐ pointed and rise straight from the vesicle wall. In the groups, the process bases are closely located or attached but without any additional structure and the groups are clearly distant from one another. Processes are hollow inside and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 370–600 μm (holotype 478 μm, paratype 600 μm); process length 17– 31 μm (holotype 31 μm, paratype 29 μm); process width about 1 μm; distance between clusters of processes 5–13 μm. Present record. – Yangtze Gorges area, Niuping, northern and southern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran. Remarks. – The diagnostic feature of the new species, and in distinction from other species of Appendisphaera, is the occurrence of processes in clusters. Otherwise, the shape of processes and their length is the same as in A. grandis but the proportion of the process length to vesicle diameter is very different because of much larger vesicle diameter in the new species. Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005 Figures 21–23 1985 Baltisphaeridium (?) strigosum Jankauskas; Pyatiletov & Rudavskaya, p. 152, pl. 63, figs 7, 9. 1989 Baltisphaeridium strigosum (Jankauskas et al. 1989) Jankauskas; Rudavskaya & Vasileva, pl. 1, figs 2–4; pl. 2, figs 1, 2. 1993 Appendisphaera grandis sp. nov.; Moczydłowska, Vidal & Rudavskaya, pp. 503–505, pl. 1, figs 1, 2, text-fig. 5A–D.

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Invalid 1998 Meghystrichosphaeridium magnificum new species Zhang, Yin, Xiao & Knoll 1998b, p. 36, fig. 10:5, 6. 2005 Appendisphaera grandis (Moczydłowska et al., 1993, emended); Moczydłowska, p. 294, figs 3, 4. 2006 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; Knoll, Javaux, Hewitt & Cohen, fig. 3 g. (Holotype reproduced from Moczydłowska et al. 1993). 2008 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Willman & Moczydłowska, pp. 519, 520, fig. 6C. 2010 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; Chen, S., Yin, C., Liu, P., Gao, L., Tang, F. & Wang, Z., fig. 2:1. 2010 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; Golubkova, Raevskaya & Kuznetsov, pl. 1, fig. 1, pl. 3, figs 4, 10. 2011 Appendisphaera grandis; Moczydłowska, Landing, Zang & Palacios, text-figs. 1C, 2A, B. 2013 Meghystrichosphaeridium magnificum Zhang, Yin L., Xiao & Knoll, 1998; Liu, P., Yin, C., Chen, S., Tang, F. & Gao, L., fig. 11 I–J. 2014 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; Xiao, S., Zhou, C., Liu, P., Wang, D. & Yuan, X., 2014a, pp. 9, 10, fig. 3:1–3. 2014 Appendisphaera magnifica (Zhang, Yin, Xiao & Knoll, 1998b) n. comb.; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M, 2014b, pp. 21, 28, figs 19.1–19.6, 20.1–6. non 2014 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; Shukla & Tiwari, p. 215, fig. 4D, E. (= A. tenuis). 2016 Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Prasad & Asher, p. 42, pl. 2, figs 3, 4.

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 20. A–G, Appendisphaera clustera n. sp. A–C, holotype, IGCAGS‐D2XFH635, thin section XFH0946‐1‐170 (D42, N: 41 × 112.4); B, enlarged fragment shown by white arrow in A; C, enlarged fragment shown by green arrow in A. D–E, paratype, IGCAGS‐D2XFH329, thin section XFH0946‐1‐43 (W21, N: 20.8 × 94.8); E, enlarged fragment shown by arrow in D. F–G, IGCAGS‐D2XFH052, thin section XFH81120‐2X‐7 (F49/2, N: 48.2 × 111); G, enlarged fragment shown by arrow in F.

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2017 Appendisphaera fragilis; Ouyang, Guan, Zhou & Xiao, fig. 8D–F. 2017 Appendisphaera magnifica; Hawkins, Xiao, Jiang, Wang & Shi, fig. 9A–B. 2017 Appendisphaera? hemisphaerica; Hawkins, Xiao, Jiang, Wang & Shi, fig. 9C–D. 2017 Appendisphaera crebra; Hawkins, Xiao, Jiang, Wang & Shi, fig. 9E–F. Material. – 98 very well‐preserved specimens including a single specimen with internal cells that are recorded for the first time in this genus (Fig. 21E). Description. – Vesicle medium to large in size, circular to oval in outline, originally spheroidal, bearing abundant homomorphic processes of almost equal length and densely distributed on vesicle wall but not attached to each other. Processes cylindrical, slightly tapering at the distal portion to sharp‐pointed tips and widened at the base. They are hollow and freely communicate with the vesicle cavity. Vesicle may have preserved within its cavity a number (4) of spheroidal internal bodies (cells) of equal diameter and arranged in three‐dimensional, planar tetrad symmetry cluster. The cells are attached to each other but are partly separated from the internal surface of the vesicle leaving small voids (Fig. 21E). Dimensions. – Vesicle diameter 50–812 μm (x = 241, δ = 213, n = 72); processes length 8–80 μm (x = 29, δ = 20, n = 65) or 7.5–42.6% of vesicle diameter (x = 17.9%, δ = 8.1%, n = 65); width of process bases 1–3 μm (n = 72). Preservation. – The exceptionally well‐preserved specimen with dividing cells (Fig. 21E) shows semi‐ transparent vesicle wall with superficial, abundant thin processes and four cells in the vesicle cavity, which have their own thick wall in comparison with this of the vesicle and dark and microgranular in appearance. The cell voids are filled in by the white– yellowish, glossy in optic appearance amorphous silica that also replaced the sediment matrix surrounding the vesicle. In other specimens, the disintegrated cells may have left the outlines of their walls or the faint ‘ghost’ geometry of decayed cells (Fig. 22C). The taphonomic states of progressive disintegration and partial preservation of the internal content of the vesicle and dividing cells are seen in a few specimens (Figs 21F, 22A, C, E, 23C). The prominent feature of decaying organic matter is its texture becoming microgranular and being aggregated into larger

FOSSILS AND STRATA

circular fragments or patchy lumps inside the vesicle (Fig. 22A, C, E). Diagenetic minerals in chert nodules (silica and berthierine, and clay minerals) precipitated in the voids and around microgranular and larger fragments of organic matter. Remarks. – The specimen of Appendisphaera grandis with internal cells (Fig. 21E) adds a vital feature to make inferences on biological affinity of the microfossil. The spheroidal internal body or multiple bodies have been preserved in ornamented vesicles of several morphotypes, i.e. form‐species of organically preserved microfossils of Ediacaran age and various Proterozoic and early Palaeozoic ages (Xiao et al. 1998; Xiao & Knoll 2000; Yin et al. 2007b; Moczydłowska et al. 2011; Liu et al. 2014b; Xiao et al. 2014a; Zhang & Pratt 2014; Agić et al. 2015; Moczydłowska 2015). In various species, they have been recognized as reproductive structures of alternatively metazoan cysts/embryos (Xiao & Knoll 2000; Knoll et al. 2006; Yin et al. 2007b; Cohen et al. 2009; Knoll 2014), holozoan cysts (Huldtgren et al. 2011), or as algal cysts (Moczydłowska et al. 2011; Zhang & Pratt 2014; Agić et al. 2015; Moczydłowska 2015). It is out of the scope of the present paper to discuss the issue of these assignments, and we study only the here recorded taxa. The genus Appendisphaera, exemplified by its type species A. grandis, has been considered as phytoplanktic, algal microfossil because of its morphologic similarity to zygotic cysts, the presence of an excystment opening (circular pylome), and the cell‐wall resistance properties as they are known in many extant microalgae (Moczydłowska 2005, 2015). The metazoan affinity of Appendisphaera as being diapause egg cyst suggested by Yin et al. (2007b), Cohen et al. (2009) and Knoll (2014) is not supported because of the presence of pylome, which is the algal cyst character (Moczydłowska 2015). The opening of cyst or vegetative cell in some heterotrophic protists morphologically defined by neck, collar or other structures differs from the algal pylome. Present record. – South China, Hubei Province, Yangtze Gorges area, the Chenjiayuanzi, Nantuocun, Wangfenggang, Niuping, northern and southern Xiaofenghe sections, member II, and the Baiguoyuan, Chenjiayuanzi, Dishuiyan, Liuhuiwan and Xiaofenghe sections, member III of the Doushantuo Formation, Ediacaran. Occurrence and stratigraphic range. – Russia, East Siberia, Khamaka Formation, Ediacaran (Moczydłowska et al. 1993; Moczydłowska 2005; Golubkova et al. 2010); Australia, Officer Basin, Giles 1 borehole, Tanana Formation, Ediacaran (Willman &

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 21. A–F, Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; emended Moczydłowska, 2005. A, IGCAGS‐WF146, thin section WFG31.2‐8 (M40/2, Z: 97.7 × 10.5). B, IGCAGS‐NXF008, thin section NXF30.1‐15 (J33/2, Z: 88 × 18.8). C, IGCAGS‐NP1‐ 023, thin section NP6‐4‐1 (M37, N: 36.2 × 104.8). D, IGCAGS‐WF147, thin section WFG31.2‐11 (U29, Z: 86 × 7). E, IGCAGS‐LHW145, thin section LHW6.6‐7 (M44/3, Z: 101.5 × 14.8). F, IGCAGS‐DSY044A, thin section DSY4.8‐7 (S20/2, Z: 79.3 × 9. Specimen shown in E preserves four cells within the vesicle cavity and represents the reproductive stage of the cyst (acanthomorphic vesicle) containing dividing cells inside. Other specimens are filled in by diagenetic opaline silica.

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Fig. 22. A–G, Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; emended Moczydłowska, 2005. A–B, IGCAGS‐ D2XFH371, thin section XFH0946‐1‐57 (P18/1, N: 17.3 × 102); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐D2XFH523, thin section XFH0946‐1‐128 (L21, N: 20.8 × 105.6); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐CJ533, thin section CJ149.5‐3 (Y24, Z: 83 × 2.8); F, enlarged fragment shown by arrow in E at different focal level. G, IGCAGS‐D2XFH674, thin section XFH0946‐1‐182 (X51/2, N: 50 × 94.5). Specimen in A preserves the internal body within the vesicle cavity that is the zygotic cell before division. Specimen in C shows organic remnants of degraded cells within the vesicle cavity, which probable formed a tetrad with three cells seen in the view plane. Specimen in G shows vesicle cavity totally replaced by diagenetic silica.

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 23. A–F, Appendisphaera grandis Moczydłowska, Vidal & Rudavskaya, 1993; emended Moczydłowska, 2005. A–B, IGCAGS‐CJ248, thin section CJ137.4‐1 (D26, Z: 84.4 × 22.7); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐JQN134, thin section 11728‐3‐3 (H26/3, N: 25.2 × 108.1); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐CJ161, thin section CJ133.1‐6 (U41/4, Z: 99.1 × 6.6); F, enlarged fragment shown by arrow in E. Specimens variously preserved and showing degraded organic matter within the vesicle cavity (A), remnants of spheroidal small cells of equal diameter in the vesicle cavity (C), or being totally filled in by silica (E).

Moczydłowska 2008); South China, Hubei Province, Zhangcunping section, Doushantuo Formation (Chen et al. 2010); northwestern Hunan Province, Lujiayuanzi section, Doushantuo Formation

(Ouyang et al. 2017); and Guizhou Province, Weng'an section, unit 4A, Doushantuo Formation (Xiao et al. 2014a). India, East Rajasthan, Chambal Valley, Lower Vindhyan Group, Ediacaran (Prasad & Asher

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2016). Northern Mongolia, the Upper Khesen Formation, uppermost Ediacaran (Anderson et al. 2017). The species has been recorded throughout the entire Ediacaran System. Appendisphaera lemniscata n. sp.

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2013 Unnamed species C; Liu, Yin, C., Chen, Tang & Gao, fig. 12G, H. 2014 Appendisphaera longispina new species; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 21, figs 17:1–5, 18:1–6.

Figure 24

2014 Appendisphaera crebra (Zang in Zang and Walter, 1992) n. comb.; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 17, figs 10:1–6, 11:1–6.

Holotype. – Specimen IGCAGS‐JQN119, thin section JQN110405–4–3, H35/3; illustrated in Figure 24A–F.

Material. – Two relatively well‐preserved specimens.

Derivation of name. – From Latin lemniscatus – adorned with ribbons; referring to ribbon‐shaped processes. Locus typicus. – Hubei Province, Yangtze Gorges area, Jiuqunao section.

Description. – Vesicle circular in outline, originally spheroidal, bearing abundant, uniform simple processes that are narrow, tubular and tapering to sharp‐ pointed tips and having small conical bases that gradually elongate into stem portion of the process. Processes are tightly distributed and some are basally joined but not all. They are hollow and freely communicate with vesicle cavity.

Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at the stratigraphic level of 43 m.

Dimensions. – Vesicle diameter 143–278 μm; overall process length 32–80 μm; width of process bases 4– 15 μm; length of process bases 4–15 μm.

Material. – A single well‐preserved specimen.

Remarks. – Liu et al. (2014b) considered the morphologic similarity between specimens that they have attributed to A. crebra and those of A. longispina, and concluded that there is no clear distinction between both taxa. The reservation remains to the taxonomic combination of A. crebra because the species crebrum by Zang (in Zang & Walter 1992b) has significantly different morphology than diagnosed for Appendisphaera. The holotype and type collection specimens originally attributed to Goniosphaeridium cerebrum Zang, 1992 (in Zang & Walter 1992b, p. 54, fig. 40F–J) show conical processes and many processes branch terminally. The species was diagnosed as having ‘long unbranched or simply branched, … blade‐like processes’. These features are dissimilar to those observed in specimens attributed to Appendisphaera crebra by Liu et al. (2014b). The species ‘Goniosphaeridium cerebrum’ should be revised because the genus is redundant and a junior synonym of Polygonium (Albani 1989; Le Hérissé 1989; Moczydłowska 1998), and the species transferred to another taxon but not Appendisphaera. The combination ‘A. crebra’ is abandoned herein and its specimens from the Doushantuo Formation are transferred to A. longispina. This revision effectively extends the vesicle diameter of A. longispina to 100– 370 μm and process length to 15–50 μm, but the diagnostic features of long, slender, uniform processes that taper gradually to sharp‐pointed tips from

Diagnosis. – Vesicle large, spheroidal, bearing abundant long, uniform in shape processes, tubular and appearing as ribbon‐shaped with short conical bases, and tapering at tips. Processes are clearly separated on equal distance, are hollow inside and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 497 μm; processes length >80 μm in (>16.1% of vesicle diameter); process width 3 μm; width of process bases 6–10 μm. Remarks. – Recognition of a new species based on observations on a single specimen has strong limitations to as infraspecific variability and taphonomic state; however, the specimen shows uniform shape of tubular processes and their conical bases. Processes are thin and of the same width along the entire process length. Present record. – Yangtze Gorges area, Jiuqunao section, Doushantuo Formation, member II, Ediacaran. Appendisphaera longispina Liu, Xiao, Yin, Chen, Zhou & Li, 2014 Figure 25

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 24. A–F, Appendisphaera lemniscata n. sp., holotype, IGCAGS‐JQN119, thin section JQN110405‐4‐3 (H35/3, N: 33.8 × 108.5). Green, white, red and blue arrows in A correspond to enlarged fragments shown in B–E, respectively. F, enlarged fragment shown by arrow in E.

conical bases is consistently observed and a single process is branching.

Appendisphaera longitubulare (Liu, Xiao, Yin, Chen, Zhou & Li, 2014) n. comb.

Present record. – South China, Hubei Province, Yangtze Gorges area, northern Xiaofenghe and Jiuqunao sections, Doushantuo Formation, member II, Ediacaran.

Figure 26

Occurrence and stratigraphic range. – South China, Hubei Province, Yangtze Gorges area, Niuping section, Doushantuo Formation, member III, Ediacaran (Liu et al. 2014b).

2014 Tanarium longitubulare new species; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 111, figs 78, 79. Material. – Four well‐preserved specimens.

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Fig. 25. A–D, Appendisphaera longispina Liu, Xiao, Yin, Chen, Zhou & Li, 2014. A–B, IGCAGS‐D2XFH112, thin section XFH81120‐2S‐6 (O23, Z: 82.5 × 12.3); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐JQN257, thin section 11922‐4‐11 (X42, N: 40.8 × 94.7); D, enlarged fragment shown by arrow in C.

Description. – Vesicle medium in size, circular in outline, originally spheroidal, bearing numerous long and homomorphic processes evenly distributed on the vesicle surface. Processes cylindrical with truncated tips and rise straight from the vesicle surface or have slightly widened basal portions but not differentiated in shape from the stem portion. Sporadically, two processes may rise from a common base. Processes are hollow and freely communicate with the vesicle cavity. The process length is approximately half or much more than the vesicle diameter. Dimensions. – Vesicle diameter 75–115 μm; process length 50–83 μm; ratio of process length to vesicle diameter 50%–91%; width of process bases 2–3 μm; distance between processes 1–3 μm (n = 4). Remarks. – The new combination and transfer of the species to the genus Appendisphaera is substantiated by the presence of very regular, tubular in shape processes, their abundance and even distribution. The strong similarity to Appendisphaera has been observed

by Liu et al. (2014b), and new material confirms a high ratio of the process length to vesicle diameter that is exceeding this ratio known in Tanarium. The present record documents wider stratigraphic range within the Doushantuo Formation and in its older member. Present record. – Hubei Province, Yangtze Gorges area, Niuping, northern and southern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran. Occurrence and stratigraphic range. – South China, Hubei Province, Yangtze Gorges area, Niuping and Wangfenggang sections, Doushantuo Formation, member III, Ediacaran (Liu et al. 2014b). Appendisphaera setosa Liu, Xiao, Yin, Chen, Zhou & Li, 2014 Figure 27 2013 Unnamed species G Liu, Yin, C., Chen, Tang & Gao, fig. 12K, L.

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 26. A–F, Appendisphaera longitubulare (Liu, Xiao, Yin, Chen, Zhou & Li, 2014) n. comb. A–B, IGCAGS‐NP1‐134, thin section NP81120‐6j (F34, N: 33.5 × 110.5); B, enlarged fragment shown by arrow in A. C, IGCAGS‐NP1‐153, thin section NP81120‐6R (U37, N: 36.2 × 96.4). D, IGCAGS‐D2XFH046, thin section XFH81120‐2X‐6 (P43/2, N: 42.2 × 102.3). E–F, IGCAGS‐D2XFH044, thin section XFH81120‐2X‐6 (M31/3, N: 30 × 104.7); F, enlarged fragment shown by arrow in E, demonstrating the bifurcating process pointed by arrow.

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2014 Appendisphaera setosa new species Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 31, figs 21:1–8, 22:1–9. Material. – Ten well‐preserved specimens. Description. – Vesicle large in size with sharp circular to oval outline, originally spheroidal, bearing evenly distributed homomorphic, delicate and thin processes of equal length. Processes tubular with blunt or round tips and rising straight from the vesicle surface. They are hollow inside and communicate with the vesicle cavity and are separated from one another on even distance. Dimensions. – Vesicle diameter 240–566 μm (x = 389 μm); process length 10–37 μm (x = 19 μm); process width 1 μm; distance between processes 2– 6 μm; ratio of process length to vesicle diameter 3.4– 8.7% (x = 5%; n = 10). Remarks. – The species is similar in an overall shape to A. tenuis, but its processes are less numerous and thinner, and they have no basal conical portions. Present record. – Yangtze Gorges area at the Baiguoyuan, Dishuiyan and Chenjiayuanzi sections, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – South China, Hubei Province, Yangtze Gorges area, Niuping and Wangfenggang sections, Doushantuo Formation, member III, Ediacaran (Liu et al. 2014b). Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993, emended Figure 28 pro parte 1992 Cymatiosphaeroides dilutopilum sp. nov.; Zang in Zang & Walter, 1992a, p. 36, fig. 32D–F. pro parte 1992 Cymatiosphaeroides pilatopilum sp. nov.; Zang in Zang & Walter, 1992a, p. 36, fig. 32A–C. pro parte 1992 Comasphaeridium sp. B Zang in Zang & Walter, 1992a, p. 34, fig. 28G. 1993 Appendisphaera? tabifica sp. nov.; Moczydłowska, Vidal & Rudavskaya, 1993, p. 508, text-fig. 6C, D.

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1997 Comasphaeridium sp.; Gravestock et al., p. 91, fig. B. 2005 Appendisphaera barbata sp. nov.; Grey, pp. 209–213, fig. 92A–G. 2005 Appendisphaera centoreticulata sp. nov.; Grey, pp. 213–215, figs 100A– D, 101A–F. 2005 Appendisphaera dilutopila (Zang in Zang & Walter 1992a) comb. nov., emend.; Grey, pp. 215–221, fig. 105A–D. 2005 Appendisphaera minutiforma sp. nov.; Grey, pp. 221–224, fig. 109A. 2006 Appendisphaera barbata Grey, 2005; Willman, Moczydłowska & Grey, p. 25. 2007 gen. et sp. indet.; Golubkova & Raevskaya, pl. 1, figs 1–3. 2008 Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993; Willman & Moczydłowska, p. 520, figs 6D–F, 8C–D. 2010 ‘Appendisphaera’ tabifica Moczydłowska, Vidal et Rudavskaya; Golubkova, Raevskaya & Kuznetsov, pl. 1, figs 5, 6. 2012 Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993; Moczydłowska & Nagovitsin, p. 11, fig. 4A, B. 2014 Appendisphaera barbata Grey, 2005; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 11, fig. 7.1, 7.2. 2016 Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993, emend Moczydłowska, 2005; Prasad & Asher, p. 42, pl. II, figs 5, 6, pl. III, figs 1, 2. 2016 Apppendisphaera? brevispina Liu, Xiao, Yin, Chen, Zhou & Li, 2014; Prasad & Asher, pp. 40, 42, pl. I, figs 5, 6 (sic! Generic name misspelled).

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 27. A–H, Appendisphaera setosa Liu, Xiao, Yin, Chen, Zhou & Li, 2014. A–B, IGCAGS‐CJ172, thin section CJ134.5‐1 (J33, Z: 91 × 17.8); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐CJ240, thin section CJ134.5‐9 (U17/4, Z: 76.3 × 6.4); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐CJ271, thin section CJ137.4‐3 (K54, Z: 111.2 × 17); F, enlarged fragment shown by arrow in E. G–H, IGCAGS‐CJ404, thin section CJ137‐3 (B27, Z: 85.2 × 24); H, enlarged fragment shown by arrow in G.

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Fig. 28. A–F, Appendisphaera tabifica Moczydłowska, Vidal & Rudavskaya, 1993, emended. A–B, IGCAGS‐WF105, thin section WFG48.3‐1 (M46/4, Z: 105 × 14.7); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐WF109, thin section WFG48.3‐1 (M33, Z: 92 × 14.5); C, the vesicle with internal spheroidal bodies interpreted to be the daughter cells; D, enlarged fragment shown by arrow in C. E, IGCAGS‐WF116, thin section WFG48.3‐1 (M40, Z: 99 × 14), specimen preserving degraded remnants of organic matter inside the vesicle. F, IGCAGS‐WF117, thin section WFG48.3‐1 (M40, Z: 99 × 13.5), specimen filled in by silica and only the vesicle wall with processes is preserved organically.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Material. – 24 relatively well‐preserved specimens. Emended diagnosis. – Vesicle small to large in size, circular to oval in outline, originally spheroidal, bearing abundant simple, thin and slender but hollow cylindrical processes that are almost equal in length. Processes are homomorphic, closely distributed or almost attached and are minimally widened at the basal portion and sharp‐pointed or blunt at their tips. Process interior freely communicate with the vesicle cavity. Vesicle may have preserved within its cavity a number of spheroidal internal bodies (cells) of equal diameter. Dimensions. – Vesicle diameter 155–209 μm (x = 183 μm, δ = 15 μm, n = 14); process length 20– 32 μm (x = 25 μm, δ = 3.5 μm, n = 14) and 10.9– 18.1% of the vesicle diameter (x = 13.6%, δ = 2.2%, n = 14); process width 1 μm. Remarks. – The species differs from other species of Appendisphaera by the abundance of processes, which are very thin, flexible and have tendency to coalesce. We emend the diagnosis by adding the presence of internal bodies within the vesicle cavity. The nature of processes being solid or hollow was difficult to observe in a single specimen from the type collection of the Khamaka Formation in Siberia (Moczydłowska, Vidal & Rudavskaya 1993), as well as the presence of membrane and therefore resulted in the provisional attribution of the species to Appendisphaera. The membrane was an artefact of preservation due to coalescence of numerous processes with disseminated organic matter. Processes although very thin are hollow and communicate with the vesicle cavity, as in the genus Appendisphaera emended by Moczydłowska (2005). The species A. barbata Grey, 2005, appears synonymous to emended herein A. tabifica, and the feature of hollow processes is better documented (Fig. 11B, D). The resemblance of both species, barbata and tabifica, has been observed and discussed (Grey 2005; pers. com. by K. Grey; Willman & Moczydłowska 2008), and we follow their synonymy. We also consider three species A. centoreticulata Grey, 2005, A. dilutopila (Zang in Zang & Walter 1992a) comb. nov., emend., Grey, 2015, and A. minutiforma Grey, 2005, as junior synonyms of A. tabifica. The poorly defined reticulate pattern on the vesicle surface in A. centoreticulata is taphonomically induced by shrinkage, and the distribution of processes is obscured by their density and not necessarily limited to the margins of polygonal fields. The species has been considered similar to A. barbata, A. minutiforma and A. tabifica by Grey (2005), and all are synonymized

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herein. The differences in vesicle dimensions and process length (long in barbata, 9–42 μm; short in minutiforma, 3–16 μm) and also related to vesicle diameter) are not so significant to establish species. Processes of A. dilutopila were described as solid and nearly cylindrical (Grey 2005) because of difficulties in observations, like in case of A. tabifica (Moczydłowska 2005), but they are thin and hollow and morphologically identical to A. tabifica. Accepting the size ranges (mostly overlapping) as less significant variations among morphotypes with identical morphology among synonymized species, the total size range for A. tabifica is 40–454 μm for vesicle diameter and 4– 42 μm for process length (compiled from Moczydłowska et al. 1993; Grey 2005; herein). Present record. – South China, Hubei Province, Yangtze Gorges area, Wangfenggang section, Doushantuo Formation, member II, Ediacaran. Occurrence and stratigraphic range. – Yakutia, Siberian Platform, Nepa–Botuoba region, Zapad 742 borehole, Khamaka Formation, Upper Vendian (Moczydłowska et al. 1993; Vendian = Ediacaran); East Siberia, Patom Uplift, Ura Formation, Ediacaran (Moczydłowska & Nagovitsin 2012). Australia, Amadeus Basin, Pertatataka Formation, Ediacaran (Zang & Walter 1992; Grey 2005), and Officer Basin, Munta 1, Observatory Hill 1, Murnaroo 1, Giles 1 boreholes, lower Ungoolya Group (Grey 2005; Willman et al. 2006; Willman & Moczydłowska 2008). Russia, NE East European Platform, Vychegda Depression, Keltminsk 1 borehole, Vychegda Formation, Lower Vendian (Veis et al. 2006). South China, Hubei Province, Yangtze Gorges area, Wangfenggang section, Doushantuo Formation, member III, Ediacaran (Li et al. 2014b). India, East Rajasthan, Chambal Valley, Lower Vindhyan Group, Ediacaran (Prasad & Asher 2016). Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005 Figures 29, 30 1992 Comasphaeridium sp. A; Zang in Zang & Walter, 1992b, p. 34, fig. 28A–C. 1992 Comasphaeridium sp. B; Zang in Zang & Walter, 1992b, p. 34, fig. 28D–J. 1993 Appendisphaera tenuis sp. nov.; Moczydłowska, Vidal & Rudavskaya, 1993, pp. 506–508, text-fig. 7.

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Fig. 29. A–F, Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993 emend. Moczydłowska, 2005. A–B, IGCAGS‐SXF059, thin section SXF2.5‐46 (R34/2, Z: 89.5 × 10.5); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐WF131, thin section WF53.7‐4 (J37/1, Z: 95.8 × 18); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐SXF067, thin section SXF2.5‐68 (P44/3, Z: 98 × 13); F, enlarged fragment shown by arrow in E. Specimens partially preserving the remnants of organic matter within the vesicle cavity (dark patches in C, E) and filled in by silica (white amorphous material in A).

non 1998 Ericiasphaera spjeldnaesii Vidal, 1990; Zhang et al. 1998b, pp. 26–28. 2004 Appendisphaera minima sp. nov.; Nagovitsin & Faizullin in Nagovitsin, Faizullin & Yakshin, p. 12, pl. 1, figs 1–3.

2005 Ericiasphaera polystacha sp. nov.; Grey, pp. 264, 265, figs 169, 170. non 2007 Appendisphaera tenuis; Yin, L. Zhu, M., Knoll, A.H., Yuan, X., Zhang, J. & Hu, J., fig. 1b.

2005 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993; Grey, pp. 224–226, fig. 113.

2008 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Willman & Moczydłowska, pp. 520, 521, fig. 7B, C.

2005 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend.; Moczydłowska, pp. 296–298, fig. 5A–F.

2008 Appendisphaera tenuis Moczydlowska; Vorobeva, Sergeev & Chumakov, fig. 2k, l (sic! Should be Moczydłowska, Vidal & Rudavskaya, 1993).

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 30. A–H, Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005. A–B, IGCAGS‐CJ219, thin section CJ134.5‐5 (G27/2, Z: 85 × 20); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐CJ233, thin section CJ134.5‐7 (F42/1, Z: 99.3 × 21); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐CJ229A, thin section CJ134.5‐6 (P38, Z: 96 × 2); F, enlarged fragment shown by arrow in E. G–H, IGCAGS‐CJ242A, thin section CJ134.5‐10 (D42/1, Z: 99 × 23); H, enlarged fragment shown by arrow in G. Specimens with cavities totally replaced by silica (G) or with only small patches of organic matter in the centre (A, C, E) but consistently preserving hollow processes with minute bases.

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2010 Appendisphaera tenuis Moczydłowska, Vidal et Rudavskaya; Golubkova, Raevskaya & Kuznetsov, pl. 1, fig. 2, pl. 3, figs 5, 6. 2011 Appendisphaeratenuis Moczydłowska, Vidal &Rudavskaya,1993,emend. Moczydłowska, 2005;Sergeev, Knoll&Vorobeva, p. 1002,fig.5.4–5.6. 2011 Cavaspina amplitudinis sp. nov. Willman; Willman & Moczydłowska, 2011, p. 25, pl. I, figs 1–6. 2014 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993 emend. Moczydłowska, 2005; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 31, fig. 23. 2014 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Xiao, S., Zhou, C., Liu, P., Wang, D. & Yuan, X., 2014a, pp. 9, 10, fig. 3.4. 2014 Appendisphaera grandis Moczydłowska et al. (1993) emend. Moczydłowska (2005); Shukla & Tiwari, p. 215, fig. 4D, E. 2015 Appendisphaera sp.; Ye, Tong, An, Tian, Zhao & Zhu, p. 48, pl. 1, figs 9–14. 2016 Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Prasad & Asher, pp. 44, pl. 3, figs 3–6. 2016 Appendisphaera fragilis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Prasad & Asher, p. 42, pl. 2, figs 1, 2. 2016 Gyalosphaeridium multispinulosum Grey, 2005; Prasad & Asher, p. 52, pl. 6, figs 3, 4. 2016 Gyalosphaeridium pulchrum Zang in Zang & Walter, 1992 emend. Grey, 2005; Prasad & Asher, p. 52, pl. 6, figs 5, 6. 2016 Tanarium anozos Willman in Willman & Moczydłowska, 2008; Prasad & Asher, pp. 54, 56, pl. 7, figs 6, 7. Material. – 21 well‐preserved specimens. Description. – Vesicle medium‐ to large‐sized, circular in outline, originally spheroidal, bearing numerous relatively short in comparison with the vesicle

FOSSILS AND STRATA

diameter and slender processes. Processes are cylindrical with minimally widened bases and sharp‐ pointed tips. They are closely and evenly distributed but separated, and although thin, they are hollow and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 87–900 μm; process length 5–50 μm; process width 2–5 μm; width of process bases 2–7 μm; distance between processes 1– 6 μm. Remarks. – Specimen of A. tenuis illustrated by Yin et al. (2007b, fig. 1b) is excluded from the synonymy because it is unrecognizable for identification at the provided magnification. This identification was questioned because of the proportions between vesicle diameter and process length (Liu et al. 2014b). The same specimen reproduced at different focus level has been attributed to Distosphaera australica (Yin et al. 2011b). We include into synonymy Ericiasphaera polystacha Grey, 2005, because of similarity of its conical and short hollow processes to those in A. tenuis, and in contrast to its diagnosed solid processes. The processes in E. polystacha holotype and in other illustrated specimens (Grey 2005) are hollow and transparent with their conical bases freely open into the vesicle cavity. The species C. amplitudinis Willman, 2011 is here considered synonymous with Appendisphaera tenuis. Subsequently, the compiled size range of A. tenuis, following the present synonymy, is very broad and the ratio of process length to vesicle diameter varies in different occurrences by 4.0–12.8%, but consistently the processes are proportionally short. Present record. – South China, Hubei Province, Yangtze Gorges area, Wangfenggang and southern Xiaofenghe sections, Doushantuo Formation, member II, and Chenjiayuanzi section, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – Yakutia, Siberian Platform, Nepa–Botuoba region, Zapad 742 drillhole, Khamaka Formation; Syugdzer Saddle region, Dyudan 291‐0 drillhole, Ediacaran (Moczydłowska et al. 1993; Moczydłowska 2005; Golubkova et al. 2010); East Siberia, Baikal‐Patom Uplift, Ura Formation, Ediacaran (Nagovitsin et al. 2004; Vorobeva et al. 2008; Golubkova et al. 2010; Sergeev et al. 2011). Australia, Amadeus Basin, Rodinga 4 borehole, Pertatataka Formation, Ediacaran (Zang & Walter 1992b; Grey 2005); Officer Basin, Munta 1, Observatory Hill 1, and Lake Maurice West 1 boreholes, lower

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Ungoolya Group, Ediacaran (Grey 2005), Murnaroo 1 borehole, Karlaya Limestone of the lower Ungoolya Group, Ediacaran (Willman et al. 2006; Willman & Moczydłowska 2011), and Giles 1 borehole, Tanana Formation, Ediacaran (Willman & Moczydłowska 2008). India, Lesser Himalaya, Outer Krol Belt, Krol ‘A’ Formation, Ediacaran (Shukla & Tiwari 2014). South China, Guizhou Province, Weng'an area, unit 4A, upper Doushantuo Formation, Ediacaran (Xiao et al. 2014a); Hubei Province, Yangtze Gorges area, member II of Doushantuo Formation at Wangfenggang section, Ediacaran (Liu et al. 2014b), and member II of Doushantuo Formation at ZK407 drillhole in Zhangcunping area, Ediacaran (Ye et al. 2015). India, East Rajasthan, Chambal Valley, Lower Vindhyan Group, Ediacaran (Prasad & Asher 2016). Northern Mongolia, the upper Khesen Formation, uppermost Ediacaran (Anderson et al. 2017). Genus Asseserium Nagovitsin & Moczydłowska, 2012 Type species. – Asseserium diversum Nagovitsin & Moczydłowska, 2012; East Siberia, Patom Uplift, Ura Formation, early Ediacaran (Moczydłowska & Nagovitsin 2012). Other species. – A. fusulentum Nagovitsin & Moczydłowska, 2012; A. pyramidalis Nagovitsin & Moczydłowska, 2012. Asseserium diversum Nagovitsin & Moczydłowska, 2012 Figure 31A, B 2007 Unnamed form 1; Vorobeva, Sergeev & Knoll, pl. 1F.

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2009 Unnamed form E; Vorobeva, Sergeev & Knoll, 2009a, fig. 9:1, 2. 2012 Asseserium diversum Nagovitsin & Moczydłowska n. sp.; Moczydłowska & Nagovitsin, p. 11, fig. 5A–D. Material. – A single well‐preserved specimen. Description. – Vesicle irregularly circular in outline, originally ovoidal, bearing a few heteromorphic processes unevenly or asymmetrically distributed over the vesicle. Processes of variable length are single conical and more tubular and multiple (3 in group) rising from a common wide base; their tips are sharp‐pointed or round. Processes are hollow and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 114 μm; process length 16 μm (14% of the vesicle diameter); width of process bases 5 μm. Remarks. – The process morphology and a wide base of the multiple processes are similar to the type material of the species although the dimensions of the present single specimen are considerably larger. The species recorded in East Siberia is only 30– 50 μm in diameter and process length is 10–16 μm (n = 4; Moczydłowska & Nagovitsin, 2012) that also shows a different ratio between the process length and vesicle diameter. The specimens of synonymous unnamed form E from the East European Platform in Russia are much larger (diameter 220–240 μm; process length 10–70 μm; n = 3; Vorobeva et al. 2009a) but asymmetrical distribution of processes and their heteromorphic shape is similar. In all occurrences the species is very rare and its full size range and variety of morphological features are not yet known. The total range of vesicle diameter is 30–

Fig. 31. A–B, Asseserium diversum Nagovitsin & Moczydłowska, 2012. IGCAGS‐CJ268, thin section CJ137.4‐3 (D36, Z: 93.5 × 22.5); same specimen shown at different focal levels. C, Asseserium fusulentum Nagovitsin & Moczydłowska, 2012. IGCAGS‐CJ242D, thin section CJ134.5‐10 (N22/4, Z: 81 × 13.7).

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240 μm, process length 10–70 μm and width of process bases 3–10.5 μm. This taxon, among many other, documents the substantial range of dimensions (‘small’ to ‘large’ in conventional assessment) and strong heteromorphy of processes and provides the evidence against the concept of defining microfossil species by size classes. The broad size range shows developmental stages of microorganisms and their growth. Present record. – South China, Hubei Province, Yangtze Gorges area, Chenjiayuanzi section, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – Russia, East European Platform, Keltminsk 1 borehole, at a depth of 2605–2647 m, Vychegda Formation, Ediacaran (Vorobeva et al. 2007, 2009a); East Siberia, Patom Uplift, Ura River section, Ura Formation, early Ediacaran (Moczydłowska & Nagovitsin 2012). Asseserium fusulentum Nagovitsin & Moczydłowska, 2012 Figure 31C 2012 Asseserium fusulentum Nagovitsin & Moczydłowska n. sp. Moczydłowska & Nagovitsin, pp. 11–13, fig. 5E, F. Material. – A single well‐preserved specimen. Description. – Vesicle medium‐sized, spindle‐shaped in outline with its two robust conical processes located on the opposite sides of the vesicle and extending gradually from the ovoidal central part. Processes are hollow and freely communicate with the vesicle cavity, and their tips are sharp‐pointed. Dimensions. – Vesicle overall diameter 124 μm including processes; vesicle central part 67 × 84 μm; processes length 20 μm; width of process bases 16– 17 μm. Remarks. – The species is very rare in occurrence and only four specimens are known from the type material of East Siberia and a single specimen recorded herein. The species identification is unequivocal because of its bipolar vesicle shape although the dimensions of the present specimen are twice as larger as in the type material. As aforementioned about other species of Asseserium, the size range of A. fusulentum is extended. The total range

FOSSILS AND STRATA

of vesicle length is 60–124 μm, vesicle width 24– 67 μm, process length 20 μm, width of process bases 16–17 μm. Present record. – South China, Hubei Province, Yangtze Gorges area, Chenjiayuanzi section, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – Russia, East Siberia, Patom Uplift, Ura River section, Ura Formation, early Ediacaran (Moczydłowska & Nagovitsin, 2012). Genus Asterocapsoides Yin L. & Li, 1978, emend. Xiao, Zhou, Liu, Wang & Yuan, 2014 Type species. – Asterocapsoides sinensis Yin L. & Li, 1978, emend. Xiao, Zhou, Liu, Wang & Yuan, 2014; South China, Hubei Province, Changyang District, Yichang area, Mt. Tianzhushan, Doushantuo Formation, Sinian (= Ediacaran) (Yin & Li 1978; holotype reported damaged and neotype from the same thin section designated by Zhang et al. 1998b; Xiao et al. 2014a). Other species. – Asterocapsoides fluctuensis n. sp.; Asterocapsoides robustus Xiao, Zhou, Liu, Wang & Yuan, 2014; Asterocapsoides wenganensis (Chen & Liu 1986) Xiao, Zhou, Liu, Wang & Yuan, 2014. Remarks. – The original diagnosis of the type species A. sinensis Yin L. & Li, 1978 stated the presence of inner thicker and denser wall within the outer, process bearing hyaline wall (Yin & Li 1978, pp. 87, 100, 101), and thus two‐walled vesicle. Zhang et al. (1998b, p. 24) emended the diagnosis of A. sinensis and defined the membrane‐like outer wall layer and the inner wall bearing processes, in effect the vesicle consisting of two wall layers. However, these authors described the location of the process bearing wall as inner and being surrounded by the membranous outer wall, in difference to the original diagnosis, or they recognized an additional outer membranous wall and abandoned the inner thick wall. Xiao et al. (2014a, p. 10, 11) provided a new emendation by stipulating the processes be relatively short, homomorphic and evenly distributed. These authors restated that the vesicle has the wall consisting of two layers, inner layer thick and dense, and outer layer translucent and bearing conical processes. Discussing this emendation, Xiao et al. (2014a) considered the presence of the inner wall as the preservation state (degraded cell or result of plasmolysis) and not diagnostic morphologically, whereas membrane‐like

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Ediacaran microfossils from the Doushantuo Formation

outer layer as a taphonomically labile feature. However, it is not convincing to assume that the thick and dense inner layer is more labile to preservation than the outer translucent (thin) and process bearing layer. Several taxa are preserved with inner walls in the same assemblage (Xiao et al. 2014a) and in other occurrences, which are recognized as showing the walls of the internal bodies representing reproductive stages (Moczydłowska 2010, 2015). From those descriptions and observations on the illustrated specimens of Asterocapsoides it appears that the vesicle, depending on the developmental stage it represents and the state of preservation, may consist of three walls (neither layers nor membranes). These are (1) the outer membranous spheroidal wall that surrounds (2) the process bearing wall, which in turn may comprise inside (3) the inner thick spheroidal (or even ornamented) wall. Following the reconstructions of the life cycle in organic‐ walled microfossils of diverse morphotypes with internal bodies (showing 2 to 3 walls of the vesicle), and the interpretation that they represent developmental cysts and endocysts or offspring cells/spores of organisms (Moczydłowska 2010, 2015; Agić et al. 2015), Asterocapsoides is not different. Regardless of possible alternative algal, holozoan or metazoan affinities of the microfossils in question, one is certain that they all represent developmental reproductive stages and, therefore, the internal bodies (defined by inner walls) are significant morphologic and functional characters. As such they should not be omitted from diagnoses of fossil taxa. The outer wall surrounding the ornamented wall, being membranous or dense, well or poorly preservable, if present is the morphologic feature useful for the diagnosis. This type of wall may be interpreted as the wall of mother cell or the zygote if it was an algal organism (Moczydłowska 2015). The best example of the Asterocapsoides morphotype with internal body is A. robustus (Xiao et al. 2014a, fig. 4:1, 2, 4) that has a spheroidal single body delimited by thick, dense and continuous wall detached from the process bearing wall. The cavity of the internal body is filled in by phosphatized organic matter granular in texture. The holotype of the species (Xiao et al. 2014a, fig. 4:3, 4) shows an even more puzzling feature that is the phosphatized organic matter in a shape of acanthomorphic body within the vesicle cavity and separated from the vesicle wall by permineralizing silica infilling the voids. This is likely a coincidental and taphonomically induced shape; however, acanthomorphic vesicles with acanthomorphic internal bodies are known among organic‐walled microfossils, such as the Silurian alga Beromia (Vavrdová 1986; Wood 1996) or

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Hoegklintia (Wood 2009; see comments by Moczydłowska 2015). The terms ‘wall, membrane and layer’ used in describing the vesicle of Asterocapsoides (among other microfossils) could be variously understood. We use the term wall as the organic, flexible or rigid layer surrounding the vesicle cavity and bearing ornamentation elements or sculpture or being non‐ ornamented. The vesicle cavity is occupied by mother cell, zygote or endocyst with offspring cells. The wall is the major element of vesicle construction. The wall may be single‐ or multilayered in its structure–ultrastructure. The term layer is restricted to the actual part of the microfossil wall ultrastructure and recognized by high magnification microscopy or in wall cross section by TEM (Moczydłowska & Willman 2009). Membrane is a thin and usually translucent organic layer that may surround the entire vesicle, extend between the vesicle processes or other surface elements or surround individual elements (Shuiyousphaeridium; Agić et al. 2015). Membrane may be single (Trachyhystrichosphaera; Butterfield et al. 1994) or multiple (Cymatiosphaeroides; Butterfield et al. 1994; Liu et al. 2014b; or Tianzhushania; Xiao et al. 2014a) and is external to the vesicle wall. In morphotypes with internal body/bodies in the vesicle cavity (like in cited above A. robustus), we recognize that they have their own wall, regardless of whether it is thin membraneous or thick and rigid (Moczydłowska 2015). We prefer to use the term wall to avoid further morphologic or functional misidentification in describing microfossils. In unicellular microfossils, it is not certain whether we observe the cell wall and cell membrane – two distinctive elements in a cell – as in some types of living cells (algal, plant and fungal), or the cyst wall and internal endocyst membrane in their developmental stages. Thus, the term vesicle wall with further determination of its location (additional outer or additional inner wall), its ornamentation (process bearing wall) or thickness (membranous, dense, rigid, translucent) will be applied in morphologic descriptions of microfossils. Morphologically recognizable, although present or absent depending on the developmental stage of the organism, or selective preservation because of its fragility vs robustness, all three walls might have been part of Asterocapsoides in its ontogenetic life cycle. Comparable morphotypes are found among microfossils of various ages, such as the Ediacaran Tanarium tuberosum and the Cambrian Polygonium varium (Moczydłowska 2015). The new combination of the species A. wenganensis (basionym Meghystrichosphaeridium wenganensis Chen and Liu, 1986) proposed by Xiao et al. (2014a,

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figs 2, 5:4–12) is taken with reservation because their new specimens are preserved without the terminal parts of the processes and thus missing one of the diagnostic features. Described as having tapering processes with pointed or slightly blunt tips they are neither documented nor were they observed in the holotype, which has also broken processes. Asterocapsoides fluctuensis n. sp. Figure 32

FOSSILS AND STRATA

Ediacaran microfossils there are taxa in scale of tens not hundreds of micrometres. The new species is morphologically typical of Asterocapsoides, but it differs from A. sinensis by having triangular processes that are proportionally longer as a function of vesicle size and from A. robustus by less numerous and proportionally wider at the base processes. A. wenganensis has widely separated processes in comparison to those of the new species, which are closely arranged and connected at their bases processes.

Holotype. – Specimen IGCAGS‐JQN252, thin section 11922‐4‐10, U29/3; illustrated in Figure 32A.

Present record. – South China, Hubei Province, Yangtze Gorges area, Jiuqunao, Jiulongwan and Wangfenggang sections, Doushantuo Formation, member II, Ediacaran.

Derivation of name. – From Latin fluctus – wave; referring to the wavy outline of the vesicle that is formed by the process shape.

Genus Bacatisphaera Zhou, Brasier & Xue, 2001, emend. Xiao, Zhou, Liu, Wang & Yuan, 2014

Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II, at a stratigraphic level of 34 m.

Type species. – Bacatisphaera baokangensis Zhou, Brasier & Xue, 2001 emend. Xiao, Zhou, Liu, Wang & Yuan, 2014; Hubei Province, Baokang County, Baizhu Phosphorite Deposit section, Doushantuo Formation, Ediacaran (Zhou et al. 2001; Xiao et al. 2014a).

Material. – 11 relatively well‐preserved specimens observed in thin sections.

Bacatisphaera sparga n. sp.

Locus typicus. – Hubei Province, Yangtze Gorges area, the Jiuqunao section.

Diagnosis. – Vesicle relatively small in size, circular in outline, originally spheroidal, bearing relatively numerous short, conical processes with round and sharp‐pointed tips. Processes densely distributed and attached to one another at their bases forming the wavy outline of the vesicle wall. Processes hollow and freely communicate with the vesicle cavity. An internal spheroidal body may be preserved within the vesicle cavity and almost entirely occupying the cavity with a narrow void left between the vesicle wall bearing processes and the internal body wall.

Other species. – Bacatisphaera sparga n. sp.

Figure 33 Holotype. – Specimen IGCAGS‐DSY060, thin section DSY7.8‐6, D45; illustrated in Figure 33A, B. Derivation of name. – From Latin spargo – rare, few; referring to less numerous and distantly located processes. Locus typicus. – Hubei Province, Yangtze Gorges area, Dishuiyan section.

Dimensions. – Vesicle diameter 31–60 μm (holotype 44 μm, x = 46 μm); processes length 3–6 μm (holotype 5 μm, x = 5 μm); width of process bases 3– 7 μm (holotype 7 μm, x = 5 μm; n = 11).

Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member III.

Remarks. – The new species is much smaller in diameter than any previously described Asterocapsoides species. The size range among Asterocapsoides species is broad, from 150 to 700 μm (Xiao et al. 2014a), and the new species ranges only 40–60 μm. This difference shows a greater variability of the taxon and demonstrates that among usually larger

Diagnosis. – Vesicle medium‐ to large‐sized, circular in outline, originally spheroidal, bearing evenly but distantly distributed small, homomorphic, hemispherical processes (protrusions) that are hollow and freely communicate with the vesicle cavity. Processes are flat and regular circular at bases and may form radial wrinkles at basal portion.

Material. – Five well‐preserved specimens.

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 32. A–D, Asterocapsoides fluctuensis n. sp. 1, holotype, IGCAGS‐JQN252, thin section 11922‐4‐10 (U29/3, N: 28.2 × 96.7). B, IGCAGS‐WF096, thin section WFG42.6‐9 (E30/2, Z: 89 × 21). C, IGCAGS‐JQN258, thin section 11922‐4‐12 (N27, N: 26.6 × 104). D, IGCAGS‐WF033, thin section WFG9.4‐19 (S43, Z: 101.5 × 9.2). Specimens with very well‐preserved processes and vesicle wall despite of diagenetic emplacement of silica into the vesicle cavity.

Dimensions. – Vesicle diameter 125–254 μm (holotype 197 μm, x = 196 μm); process length 2–3 μm; width of process bases 2–5 μm (holotype 2 μm); distance between processes 2–15 μm (holotype 2– 12 μm; n = 5). Remarks. – The new species is characterized by very small processes (rather dome‐shaped protrusions) that are distantly located in comparison with those in Bacatisphaera baokangensis, which are closely located and larger.

The type species B. baokangensis has been studied by scanning electron microscope (SEM) in extracted phosphatized specimens (Zhou et al. 2001; Xiao et al. 2014a), and by light microscope (LM) in thin sections (Liu et al. 2014b). This preservation may cause uncertainty in morphologic comparison with other genera, such as Pustulisphaera and Eotylotopalla, or specimens preserved organically and extracted from the sediment. B. baokangensis has very limited record of altogether 10 specimens in three localities (Zhou et al. 2001; Liu et al. 2014b;

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Fig. 33. A–I, Bacatisphaera sparga n. sp. A–B, holotype, IGCAGS‐DSY060, thin section DSY7.8‐6 (D45, Z: 103.1 × 22.6); B, enlarged fragment shown by arrow in A with sectioned hemispherical processes. C–E, IGCAGS‐DSY070, thin section DSY8‐16 (D51/1, Z: 108.3 × 23.2); D–E, enlarged fragments shown by arrow in C at different focal levels. F–G, IGCAGS‐DSY077, thin section DSY8‐20 (N22/ 2, Z: 81 × 14); G, enlarged fragment shown by arrow in F. H–I, IGCAGS‐CJ351, thin section CJ151.8‐6 (M34, N: 33.2 × 105.2); I, enlarged fragment shown by arrow in H.

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Ediacaran microfossils from the Doushantuo Formation

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Xiao et al. 2014a), whereas P. membranacea (of monospecific genus) only 4 specimens and only one (the holotype) illustrated (Zhang et al. 1998b). The likely synonymy of Bacatisphaera and Pustulisphaera (Xiao et al. 2014a; Liu et al. 20124b) was suggested because of the remarkable similarity of hemispherical processes but distinguishing of the genera has been based on the presence of outer membranous wall layer in Pustulisphaera diagnosed by Zhang et al. (1998b). Eotylotopalla Yin, 1987 has morphologically comparable processes and lacks the outer wall but it was considered a distinct genus because of its small vesicle (35–85 μm in diameter among its three species) and different proportion of the process length to vesicle diameter (Liu et al. 2014b; Xiao et al. 2014a).

The early Palaeozoic genus Goniosphaeridium is a junior synonym of Polygonium (Albani 1989; Le Hérissé 1989; Moczydłowska 1998) and is diagnosed by polygonal outline of the vesicle that is formed by the wide conical process bases. Processes are long conical with sharp‐pointed tips. This characteristic is not adequate to any group of specimens: neither attributed to G. crebrum Zang, 1992 nor B.? crebrus (Zang, 1992) Grey, 2005. Both morphologically differing groups should be transferred to appropriate genera.

Present record. – Yangtze Gorges area, Chenjiayuanzi and Dishuiyan sections, DoushantuoFormation,memberIII,Ediacaran.

1992 Briareus borealis sp. nov.; Knoll, pp. 764, 765, pl. 5, figs 3, 4.

Genus Briareus Knoll, 1992 Type species. – Briareus borealis Knoll, 1992, from Svalbard, Scotia Group, chert nodules of the Baklia Formation, Vendian (= Ediacaran) (Knoll 1992). Other species. – Non Briareus? crebrus (Zang, 1992) Grey, 2005; Briareus robustus n. sp.; Briareus vasformis n. sp. Remarks. – The taxonomic combination Briareus? crebrus (Zang, 1992) emend., comb. nov. by Grey (2005, pp. 230–232) is not followed here because this taxon does not show the generic diagnostic features. The genus Briareus Knoll, 1992 is characterized by having hollow and cylindrical processes that flare at both base and apex, and freely communicate with the vesicle cavity (Knoll 1992). The processes of type species B. borealis Knoll, 1992 have small conical bases and small funnel‐shaped tips of processes. Processes are relatively short, numerous but clearly distant from one another. Goniosphaeridium crebrum Zang, 1992 (Zang in Zang & Walter, 1992b, fig. 40F– J), transferred to Briareus? crebrus by Grey (2005), has heteromorphic processes, which are conical that taper towards sharply pointed tips and cylindrical with divided tips. Processes are longer in relation to the vesicle diameter and more abundant than in Briareus. Specimens of B.? crebrus (Grey 2005, fig. 121A, B) show conical processes tapering to blunt tips but not flaring. Neither G. crebrum Zang, 1992 nor B.? crebrus (Zang 1992) Grey, 2005 could be accommodated in Briareus.

Briareus borealis Knoll, 1992 Figure 34

1995 Briareus borealis; Yin, C. & Gao, pl. 2, fig. 11. 2014 Briarcus sp.; Liu, Chen, Zhu, Li, Yin & Shang, 2014a, fig. 7C (sic! should be Briareus). Material. – 13 relatively well‐preserved specimens. Description. – Vesicle circular in outline, originally spheroidal, bearing evenly distributed and relatively short, robust processes having small conical bases and flared tips. Processes are cylindrical in their central portion or constricted between conical bases and funnel‐shaped terminations. They are hollow and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 193–250 μm (x = 223 μm; n = 13); processes length 15–27 μm (x = 22 μm, n = 29); process width 3–12 μm (x = 6 μm, n = 29); width of process bases 11–21 μm (x = 15 μm, n = 29); width of process tip 6–17 μm in (x = 10 μm, n = 29); distance between processes 1– 15 μm (x = 7 μm; n = 23); ratio of process length to vesicle diameter 6.5–14% (x = 9.7%, n = 29). Remarks. – The type species B. borealis Knoll, 1992 has been recognized by study of a single specimen, yet the diameter given in its diagnosis was 100–200 μm (Knoll 1992, fig. 5.3). This holotype is circular in outline and calculated from the illustration to be ca 120 × 130 μm in diameter. The present specimens are larger but the ratio of the process length to vesicle diameter is similar, and the overall body plan and morphology of processes are the same.

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Fig. 34. A–F, Briareus borealis Knoll, 1992. A–B, IGCAGS‐CJ111, thin section CJ71.6‐10 (O31/4, N: 30.7 × 102.5); B, enlarged fragment of the vesicle upper part in A. C, IGCAGS‐CJ095, thin section CJ71.6‐3 (Q28, N: 27.8 × 101). D, IGCAGS‐CJ092, thin section CJ71.6‐1 (W39, N: 38.4 × 95). E, IGCAGS‐CJ102, thin section CJ71.6‐4 (U44, N: 43.1 × 96.9). F, IGCAGS‐CJ097, thin section CJ71.6‐4 (K38, N: 37.4 × 106.7).

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Present record. – Yangtze Gorges area, Chenjiayuanzi and Jiulongwan sections, Doushantuo Formation, member II, Ediacaran. Occurrence and stratigraphic range. – Svalbard, Scotia Group, Baklia Formation, Vendian (= Ediacaran) (Knoll, 1992). South China, Hubei Province, Changyang area, Liuxi section, Doushantuo Formation, Sinian (= Ediacaran) (Yin & Gao 1995), and Yangtze Gorges area, Chenjiayuanzi section, Doushantuo Formation, member II, Ediacaran (Liu et al. 2014a). Briareus robustus n. sp. Figure 35 Holotype. – Specimen IGCAGS‐JQN120, thin section 110405–4–3, N37/3; illustrated in Figure 35A–C. Derivation of name. – From Latin robustus – hard and strong like oak, robust; referring to appearance of the vesicle with large and robust processes. Locus typicus. – Hubei Province, Yangtze Gorges area, Jiuqunao section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at a level of 42 m.

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Material. – A single well‐preserved specimen. Diagnosis. – Vesicle oval in outline, originally spheroidal, bearing short, robust tubular and more conical processes with prominent conical bases and flared terminations. Processes are tightly distributed and attached at their bases to one another. They are hollow and communicate freely with the vesicle cavity. Process tips are in the shape of small funnels or are blunt. Process cross sections are circular to oval. Dimensions. – Vesicle diameter 342 μm; process length 68 μm (17% of the vesicle diameter); width of process stem 8–18 μm; width of process bases 23– 48 μm; width of process terminations 11–32 μm. Remarks. – A single specimen may not provide adequate features to describe a new species; however, it differs from other species of Briareus by having larger processes that are attached at their bases and have wider stem portions of the processes. Briareus vasformis n. sp. Figure 36 Holotype. – Specimen IGCAGS‐DSY221A, thin section DSY12‐20, O35/3; illustrated in Figure 36A, B.

Fig. 35. A–C, Briareus robustus n. sp., holotype, IGCAGS‐JQN120, thin section 110405‐4‐3 (N37/3, N: 36 × 103.6); B–C, enlarged fragments shown by black and blue arrows in A, respectively.

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Fig. 36. A–H, Briareus vasformis n. sp. A–B, holotype, IGCAGS‐DSY221A, thin section DSY12‐20 (O35/3, Z: 93 × 12.4); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐DSY224, thin section DSY12.2‐9 (D34, Z: 92 × 22.6); D, enlarged fragment shown by arrow in C, and arrow points to flared termination of process. E–F, IGCAGS‐DSY230H, thin section DSY12.2‐9 (E28/1, Z: 86 × 22); F, enlarged fragment shown by arrow in E, and arrow points to process tip. G–H, IGCAGS‐230G, thin section DSY12.9‐9 (E28/1, Z: 86 × 22), H, enlarged fragment shown by arrow in G, and additional arrows indicate widened process tips.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Derivation of name. – From Latin vas, vasis – vase, vessel; referring to the overall shape of processes resembling elongated vases. Locus typicus. – Hubei Province, Yangtze Gorges area, Dishuiyan section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member III. Material. – 21 well‐preserved specimens. Diagnosis. – Vesicle small‐ to medium‐sized, circular to oval in outline, originally spheroidal, thin‐walled and bearing numerous, evenly distributed processes of almost equal length. Processes cylindrical or slightly tapering towards flared terminal parts with blunt tips and have small conical bases that rise gradually from the vesicle wall. They are hollow and freely communicate with the vesicle cavity. Processes are clearly separated from one another by similar distances. Dimensions. – Vesicle diameter 66–127 μm (holotype 99 μm; x = 99 μm, n = 17); process length 13– 21 μm (holotype 18 μm; x = 17 μm, n = 18); process width ~1 μm; width of process bases 4–10 μm (x = 7 μm; n = 18); width of process tip 2–3 μm (holotype 3 μm); ratio of process length to vesicle diameter is 13–26% (holotype 19%, x = 17.5%, n = 17). Remarks. – Depending on the state of preservation, some processes may be constricted in the stem part or taper from the base to the tip but mostly processes are cylindrical. The new species differs from B. borealis by proportionally longer and thinner processes and appearing to be much slender than those short and robust processes in B. borealis. The organic matter shrivelled in the vesicle cavity (Fig. 36A, B) appears to be a degraded content of the cell and similar preservation is seen in the holotype of B. borealis (Knoll 1992, pl. 5, fig. 3). Present record. – Yangtze Gorges area, Dishuiyan section, Doushantuo Formation, member II, Ediacaran.

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Calyxia xandaros Willman, 2008 Figure 37 Nomina nuda 2007 Calyxia xandaros; Willman, fig. 3:12. 2008 Calyxia xandaros Willman, sp. nov.; Willman & Moczydłowska, p. 521, figs 4A–F, 5A, B. Material. – Two well‐preserved specimens. Description. – Semi‐spherical, cup‐shaped vesicle with round pole and open at the opposite side, where the vesicle wall splits into a few elongate petal extensions. The extensions are concave towards the vesicle cavity or flat, almost constant in width and taper towards terminations, which are sharp‐pointed or rounded. Dimensions. – Cup‐like vesicle length is 70–85 μm; length of extensions is 80–95 μm and their width 25–30 μm. Remarks. – The vesicle extensions seem to fit the spheroidal shape of the entire vesicle (originally) while they were aligned together. Four such extensions are observed herein in a side view, two on sides and two superimposed in the central part of the vesicle (Fig. 37 A), or two on the right side and two superimposed on the left side (Fig. 37B). In species diagnosis there are 4–10 extensions reported. The extensions face one direction but may differ in their angle of opening, like petals in the tulip flower. The opening is interpreted to be the excystment structure, and the vesicle may represent a cyst at the mature stage of microorganism. Present record. – South China, Yangtze Gorges area, Chenjiayuanzi and Dishuiyan sections, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – South Australia, Officer Basin, Giles 1 and Munta 1 boreholes, Tanana Formation, Ediacaran, zones 2 and 3 (Willman & Moczydłowska 2008).

Genus Calyxia Willman, 2008

Genus Cavaspina Moczydłowska, Vidal & Rudavskaya, 1993

Type species. – Calyxia xandaros Willman, 2008 in Willman & Moczydłowska, 2008; from South Australia, Officer Basin, Giles 1 borehole at a depth of 481.15 m, Tanana Formation, zones 2–3 (Willman & Moczydłowska, 2008). The genus is monospecific.

Type species. – Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; from the Siberian Platform, Torgo G‐2 borehole, at a depth of 70–74 m, Torgo Formation, Ediacaran (Moczydłowska et al. 1993; Moczydłowska 2005).

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Fig. 37. A–B, Calyxia xandaros Willman, 2008. A, IGCAGS‐CJ283B, thin section CJ137.4‐3 (H44, Z: 101.5 × 19). B, IGCAGS‐DSY257, thin section DSY12.6‐7 (R44, Z: 101.6 × 10). Specimens with widely opened petal‐like extensions of the vesicle.

Other species. – Non C. amplitudinis Willman, 2011 in Willman & Moczydłowska, 2011; C. basiconica Moczydłowska, Vidal & Rudavskaya, 1993; C. conica n. sp.; C. uria (Nagovitsin & Faizullin, 2004 in Nagovitsin, Faizullin & Yakshin, 2004) Nagovitsin & Moczydłowska, 2012 in Moczydłowska & Nagovitsin, 2012. Remarks. – The species C. amplitudinis Willman, 2011 is here considered synonymous with Appendisphaera tenuis. The shape of processes is similar or identical in both species and the abundance of processes in C. amplitudinis, their length and flexibility is more like in the genus Appendisphaera than Cavaspina. Similarity to A. tenuis has been observed but the recognition of a new species has been based on a very different size ratio of the vesicle diameter to process length (Willman & Moczydłowska, 2011). C. amplitudinis has large vesicle diameter (500–900 μm) in comparison with the vesicle diameter reported in A. tenuis (87–143 μm, 115–147 μm in the Siberian Platform, Moczydłowska et al. 1993, Moczydłowska 2005; 415 μm in Australia, Grey 2005; and herein 370 μm). This may document a broader range of dimensions in A. tenuis, if synonymized with C. amplitudinis, and depending of the vesicle dimensions the proportions of process length will also differ. Grey (2005) recorded specimens of A. tenuis twice or so larger than in the Siberian material but with some overlap in sizes. The compiled size range of A. tenuis, following the present synonymy, is as follows: vesicle diameter 87–900 μm, process length 5–50 μm and the ratio of process length to vesicle diameter varies in different occurrences by ca. 4–10%, but consistently the processes are proportionally short.

Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993 Figure 38 1989 Unnamed specimen; Rudavskaya & Vasileva, pl. 1, fig. 5. 1989 Baltisphaeridium pilosiusculum Jankauskas; Rudavskaya & Vasileva, pl. 2, figs 4–6. 1989 Baltisphaeridium sp.; Rudavskaya & Vasileva, pl. 2, fig. 7. 1991 Baltisphaeridium (?) acuminata Kolosova sp. nov.; Kolosova, pp. 57, 58, fig. 4:1–3. 1993 Cavaspina acuminata (Kolosova, 1991) comb. nov.; Moczydłowska, Vidal & Rudavskaya, 1993, pp. 509, 510, text-fig. 10A, B. 1998 Goniosphaeridium acuminatum (Kolosova) new combination; Zhang, Yin, Xiao and Knoll 1998b, pp. 28, 32, fig. 8.3. 1999 Three-dimensionally preserved spinose microsphere; Yin, L., Xue, Y. & Yuan, X., pl. 2A, B. pro parte 2001 Meghystrichosphaera chadianensis (Chen & Liu, 1986) Zhang, Yin, Xiao & Knoll, 1998; Zhou, C., Brasier, M.D. & Xue, Y., p. 1166, pl. 2, figs 5, 6.

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Fig. 38. A–B, Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993. A, IGCAGS‐CJ166, thin section CJ133.1‐9 (U34/2, Z: 93.4 × 7.3). B, IGCAGS‐CJ143A, thin section CJ129.6‐9 (K33/2, Z: 91.5 × 16.5). Specimens demonstrate hollow short processes communicating freely with the vesicle cavity.

2002 Goniosphaeridium acuminatum (Kolosova, 1991) Zhang, Yin, Xiao & Knoll, 1998; Yuan, X., Xiao, S., Yin, L., Knoll, A.H., Zhou, C. & Mu, X., pp. 74, 75, fig. 99. 2004 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Nagovitsin, Faizullin & Yakshin, p. 12, pl. 2, figs 7, 8. 2005 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Moczydłowska, pp. 298, 299, fig. 6A, B. 2006 Cavaspina acuminata (Kolosova) emend. Moczydlovska; Veis, Vorobeva & Golubkova, pl. I, figs 5, 6, pl. II, fig. 1. 2007 Cavaspina acuminata Kolosova; Vorobeva et al., pl. IE. 2007 Goniosphaeridium acuminatum (Kolosova, 1991) Zhang, Yin, Xiao & Knoll, 1998; Yin, C., Liu, Y., Gao, L., Wang, Z., Tang, F. & Liu, P., pl. 6, figs 1, 2. 2008 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Willman & Moczydłowska, p. 522, fig. 9C.

2009 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Vorobeva, Sergeev & Knoll, 2009a, p. 177, fig. 7:11. 2011 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Willman & Moczydłowska, pp. 24, 25, pl. 2, fig. 3. non 2011 Cavaspina cf. Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Sergeev, Knoll & Vorobeva, p. 1003, fig. 10.2. 2012 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Moczydłowska & Nagovitsin, pp. 13, 14, fig. 4C, E, F. 2013 Acritarch clusters; Yin, Z., Zhu, M., Tafforeau, P., Chen, J., Liu, P. & Li, G., fig. 9J–L. 2014 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Xiao, S., Zhou, C., Liu, P., Wang, D. & Yuan, X., 2014a, p. 16, fig. 7:1–6. 2014 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 44, fig. 27:1, 2.

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2014 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Shukla & Tiwari, p. 216, fig. 5C, D. 2016 Cavaspina acuminata (Kolosova, 1991) Moczydłowska, Vidal & Rudavskaya, 1993; Prasad & Asher, p. 46, pl. IV, figs 5, 6.

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2014). South China, Guizhou Province, Weng'an area, upper Doushantuo Formation, unit 4B, Ediacaran (Zhou et al. 2001; Xiao et al. 2014a); Hubei Province, Yangtze Gorges area, upper Doushantuo Formation, terminal Proterozoic (Zhang et al. 1998b), and Xiaofenghe section, Doushantuo Formation, member III, Ediacaran (Liu et al. 2014b). India, East Rajasthan, Chambal Valley, Lower Vindhyan Group, Ediacaran (Prasad & Asher 2016).

Material. – Six well‐preserved specimens. Description. – Vesicle circular to oval in outline (originally spheroidal), bearing relatively numerous conical processes with sharp‐pointed tips, which are short, thorn‐like but hollow inside and communicate with vesicle cavity. Processes are irregularly distributed on vesicle surface. Dimensions. – Vesicle diameter 61–115 μm (x = 90 μm); processes length 15–21 μm (x = 17 μm) that is 13.4–24.5% of the vesicle diameter; width of process bases 3–6 μm (x = 4 μm); processes are spaced at 3–20 μm; n = 6. Present record. – Yangtze Gorges, Baiguoyuan, Chenjiayuanzi and Dishuiyan sections, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – Yakutia, Siberian Platform, Berezov Depression, borehole Torgo G‐2, at a depth of 70.0–74.0 m, Torgo Formation (Kolosova 1991); Nepa–Botuoba region, Talakan 806 borehole, at the interval of 1467.0– 1473.9 m, Khamaka Formation; Lena‐Anabar Depression, Charchyk 1 borehole, at the interval of 2683.0–2712.3 m, Turkut Formation, Ediacaran (Moczydłowska et al. 1993; Moczydłowska 2005); East Siberia, Patom Uplift, Ura River section, Ura Formation, Baikal Stage, late Riphean (Nagovitsin et al. 2004), restudied and evaluated as early Ediacaran (Moczydłowska & Nagovitsin 2012). Russia, NE East European Platform, Vychegda Depression, Keltminsk 1 borehole, Vychegda Formation, Upper Vendian (Veis et al. 2006; Vorobeva et al. 2007) or middle Ediacaran (Vorobeva et al. 2009). Australia, Officer Basin, Giles 1 borehole, Tanana Formation, Ediacaran (Willman & Moczydłowska 2008), and Lake Maurice West 1 borehole, Lower Ungoolya Group, Dey Dey Mudstone, Ediacaran (Willman & Moczydłowska 2011). India, Lesser Himalaya, Outer Krol Belt, Krol A Formation, Ediacaran (Shukla & Tiwari

Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993 Figure 39 1980 Baltisphaeridium? strigosum Jankauskas, 1976; Pyatiletov, p. 11, pl. 1, figs 5–8, pl. 2, figs 1–4. 1985 Baltisphaeridium? strigosum Jankauskas, 1976; Pyatiletov & Rudavskaya, p. 152, pl. 63, fig. 8. 1989 Baltisphaeridium strigosum Iank; Rudavskaya & Vasileva, pl. 1, figs 2–4, 6; pl. 2, figs 1, 2. nomen nudum 1991 Tanarium perfectum Kolosova; Kolosova, fig. 6:1–6. pro parte 1992 Comasphaeridium sp. B; Zang & Walter, 1992b, p. 34, fig. 28F, G. 1993 Cavaspina basiconica sp. nov.; Moczydłowska, Vidal & Rudavskaya, pp. 510–512, textfig. 11. invalid 1998 Meghystrichosphaeridium perfectum (Kolosova) new combination; Zhang, Y., Yin, L., Xiao, S. & Knoll, A.H., 1998b, p. 36, fig. 10:8. 2005 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Moczydłowska, pp. 300, 301, fig. 6C. 2005 Gyalosphaeridium basiconicum (Moczydłowska, Vidal & Rudavskaya, 1993) comb. nov.; Grey, p. 277 pl. I, figs 3, 4.

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 39. A–H, Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993. A–B, IGCAGS‐CJ312, thin section CJ137.4‐8 (N35/4, Z: 93.3 × 13.7); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐LHW308, thin section LHW13.8‐3 (J43/4, Z: 39.2 × 17.2); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐CJ304A, thin section CJ137.4‐6 (F49, Z: 107 × 21); F, enlarged fragment shown by arrow in E. G–H, IGCAGS‐DSY037, thin section DSY4.5‐12 (Q22/1, Z: 80.2 × 11.3); H, enlarged fragment shown by arrow in G. Specimens at different state of preservation and partially or almost entirely filled in by silica but persistently showing the conical process bases of similar dimensions.

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2005 Gyalosphaeridium multispinulosum sp. nov.; Grey, pp. 273– 277, figs 179A–D, 180A–E. 2006 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Willman, Moczydłowska & Grey, pp. 26, 27, pl. 1, figs 3, 4. 2007 Meghystrichosphaeridium perfectum (Kolosova, 1991) Zhang, Yin, Xiao, and Knoll, 1998; Yin, C., Liu, Y., Gao, L., Wang, Z., Tang, F. & Liu P., pl. 11, fig. 5. 2008 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Willman & Moczydłowska, pp. 522, 523, fig. 9D–F. 2009 Meghystrichosphaeridium ‘perfectum’ (Kolosova, 1991) Zhang, Yin, Xiao & Knoll, 1998; McFadden, Xiao, Zhou & Kowalewski, p. 183, fig. 5D. 2011 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Willman & Moczydłowska, p. 25, pl. II, figs 1, 2. 2014b Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Xiao, S., Zhou, C., Liu, P., Wang, D. & Yuan, X., 2014a, pp. 16, 17, fig. 8. 2014 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Liu, P., Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 44, fig. 27:3–6.

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Material. – 34 specimens, well‐preserved and in various state of preservation. Description. – Vesicle circular to oval in outline (originally spheroidal), bearing densely distributed processes approximately equal in length, which are conical in basal part and slender at distal part with sharp‐pointed or blunt tips. Processes are hollow and communicate with vesicle cavity. Dimensions. – Vesicle diameter 171–352 μm (x = 246 μm, δ = 41 μm); process length 7–27 μm (x = 14 μm, δ = 5 μm) or 3.3–9.1% of the vesicle diameter (x = 5.8% of the diameter, δ = 1.7%); width of process bases 3–7 μm (x = 5 μm, δ = 1.4 μm); processes spaced at 1–5 μm; n = 34. Remarks. – The total size range of the species is extended by the previous record from China (Liu et al. 2014b) and the present material, while specimens from the Khamaka Formation in the type locality of the Siberian Platform in Yakutia were smaller in diameter. The Siberian specimens were few and vesicle diameter measured 85–110 μm, process length 9– 13 μm and width of process bases 3–5 μm (Moczydłowska 2005). Together compiled, the vesicle diameter is 85–385 μm, process length 9–50 μm and width of process bases 3–7 μm. The identification of a single specimen of ?Cavaspina basiconica from the Lujiayuanzi section in the Hunan Province (Ouyang et al. 2017) is likely correct and this occurrence extends the species range into member II (Fig. 15). The record of C. basiconica in the units 4A and 4B of the Weng'an section (Xiao et al. 2014a) is interpreted here as belonging to the member II. Both records support the stratigraphic range of the species to be across members II and III of the Doushantuo Formation.

2014 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993; Shukla & Tiwari, pp. 216, 217, fig. 5E, F.

Present record. – South China, Hubei Province, Yangtze Gorges area, Chenjiayuanzi, Dishuiyan and Liuhuiwan sections, Doushantuo Formation, member III, Ediacaran.

2016 Cavaspina basiconica Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005; Prasad & Asher, p. 46, pl. IV, figs 7, 8.

Occurrence and stratigraphic range. – Yakutia, Siberian Platform, Byuk 715 borehole, Kursov Formation (Pyatiletov & Rudavskaya 1985); Nepa– Botuoba region, Zapad 742 and Talakan 823 boreholes, Khamaka Formation, Ediacaran (Moczydłowska et al. 1993; Moczydłowska 2005). Australia, Amadeus Basin, Rodinga 4 borehole, Pertatataka Formation, Ediacaran (Zang & Walter 1992b); Officer Basin, Murnaroo 1, Giles 1 and Lake Maurice West 1 boreholes, lower Ungoolya

2017 ?Cavaspina basiconica; Ouyang, Guan, Zhou & Xiao, fig. 8A–C. 2017 Cavaspina? basiconica; Anderson et al. fig. 3B–C.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Group, Ediacaran (Willman et al. 2006; Willman & Moczydłowska 2008, 2011). India, Lesser Himalaya, Outer Krol Belt, Krol A Formation, Ediacaran (Shukla & Tiwari 2014), and East Rajasthan, Chambal Valley, Lower Vindhyan Group, Ediacaran (Prasad & Asher 2016). South China, Guizhou Province, Weng'an area, Doushantuo Formation, units 4A and 4B, ca. 580–600 Ma (Xiao et al. 2014a); Hubei Province, Changyang area, Liuxi section, Lower Doushantuo Formation (Yin et al. 2007b), and Yangtze Gorges area, Tianjiayuanzi section, upper Doushantuo Formation (Zhang et al. 1998b; McFadden et al. 2009), Wangfenggang and Niuping sections, Doushantuo Formation, member III, Ediacaran (Liu et al. 2014b); northwestern Hunan Province, Lujiayuanzi section at the level 40 m (Ouyang et al. 2017), here considered to belong to the member II. Northern Mongolia, the upper Khesen Formation, uppermost Ediacaran (Anderson et al. 2017). Cavaspina conica n. sp. Figure 40 Holotype. – Specimen IGCAGS‐D2XFH663, thin section XFH0946‐1‐178, M42/3; illustrated in Figure 40A, B. Derivation of name. – From Latin conus – cone, referring to very regular conical shape of processes. Locus typicus. – Yangtze Gorges area, northern Xiaofenghe section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at a level of 113 m of the northern Xiaofenghe section. Material. – 10 well‐preserved specimens. Diagnosis. – Vesicle circular to oval in outline, originally spheroidal, bearing abundant and closely distributed conical processes, which are uniform and very regular in shape and gradually taper from wide bases to tubular terminal portions with blunt tips. Processes are short, hollow inside and freely communicate with vesicle cavity. Dimensions. – Vesicle diameter 44–71 μm (holotype 57 μm, x = 50 μm, δ = 8.3 μm); process length 3– 9 μm (holotype 5 μm, x = 4.5 μm, δ =1.5 μm) or 5– 17% of the vesicle diameter (holotype 8.8%, x = 10.3%, δ = 3.3); width of process bases 1–2 μm (holotype 2 μm, x = 1.5 μm, δ = 0.5 μm); n = 10.

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Remarks. – The new species is similar to C. basiconica in overall by having conical processes but it differs by more uniform shape of the processes with transitional change of the width between the basal and terminal portions, in contrast to those in C. basiconica having clearly distinguished bases. This could be however preservation feature because of the preservation mode in chert and due to the silica impregnation resulting in stiff appearance and more gradually changing width of processes not being collapsed. The vesicle diameter of the new species is below the range of C. basiconica, which is at the minimum 85 μm (Moczydłowska 2005). Present record. – South China, Hubei Province, Yangtze Gorges area, northern and southern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran. Genus Cymatiosphaeroides Knoll, 1984, emend. Knoll, Swett & Mark, 1991 Type species. – Cymatiosphaeroides kullingii Knoll, 1984, emend. Butterfield, Knoll & Swett, 1994; from Svalbard Archipelago, Nordaustlandet, the Hunnberg Formation, late Precambrian, ca. 750–800 Ma (Knoll 1984; Butterfield et al. 1994), currently the Tonian in age. Other species. – C. forabilatus n. sp.; C. yinii Yuan and Hofmann, 1998. Cymatiosphaeroides forabilatus n. sp. Figure 41 Holotype. – Specimen IGCAGS‐D2XFH212, thin section XFH0946‐1‐10, M60/3; illustrated in Figure 41A, B. Derivation of name. – From Latin forabilis – penetrable, referring to the processes that penetrate the vesicle outer wall. Locus typicus. – Yangtze Gorges area, northern Xiaofenghe section. Stratum typicum. – Chert nodules of the Doushantuo Formation, member II at a level of 113 m in northern Xiaofenghe section. Material. – Six well‐preserved specimens.

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FOSSILS AND STRATA

Fig. 40. A–G, Cavaspina conica n. sp. A–B, holotype, IGCAGS‐D2XFH663, thin section XFH0946‐1‐178 (M42/3, N: 40.5 × 105); B, enlarged fragment shown by arrow in A. C, IGCAGS‐D2XFH625, thin section XFH0946‐1‐165 (X19, N: 18.8 × 94). D–E, IGCAGS‐ZHU‐ XFHD2‐032, thin section XFH108‐1‐4 (M29/2, N: 28.7 × 105); E, enlarged fragment shown by arrow in D. F, IGCAGS‐D2XFH462, thin section XFH0946‐1‐108 (K58, N: 56.5 × 107.5). G, IGCAGS‐D2XFH374, thin section XFH0946‐1‐59 (E35, N: 34.4 × 111.2). Specimens in A and D show sections of vesicles that were collapsed or compressed at the lower parts and thus exhibit the processes on the vesicle surface not only on the outline.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

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Fig. 41. A–H, Cymatiosphaeroides forabilatus n. sp. A–B, holotype, IGCAGS‐D2XFH212, thin section XFH0946‐1‐10 (M60/3, N: 58 × 104.6); B, enlarged fragment shown by arrow in A. C–D, IGCAGS‐D2XFH525, thin section XFH0946‐1‐129 (H21, N: 20.4 × 108.6); D, enlarged fragment shown by arrow in C. E–F, IGCAGS‐D2XFH465, thin section XFH0946‐1‐108 (T48/2, N: 47.5 × 98.2); F, enlarged fragment shown by arrow in E. G–H, IGCAGS‐D2XFH225, thin section XFH0946‐1‐11 (N44/2, N: 43.3 × 104.3); H, enlarged fragment shown by arrow in G. The enlargements of vesicle fragments of each specimen demonstrate the two concentric walls and processes penetrating the outer wall.

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Diagnosis. – Vesicle spheroidal, large in size, consisting of two concentric walls: the inner thick wall bearing numerous, thin, solid cylindrical processes, and the outer thin, single‐layered wall surrounding the vesicle with processes half way along their length. Processes penetrate the outer wall and extend freely above its surface. Processes are regularly distributed at a constant distance from one another. Dimensions. – Vesicle diameter 280–446 μm (holotype 407 μm, x = 386 μm); process length 7–12 μm (holotype 11 μm, x = 9.5 μm) or 1.6–4.4% of the vesicle diameter (holotype 2.7%, x = 2.5% of the diameter); process width ˂ 1 μm; processes spaced at a distance of 2–7 μm; outer vesicle wall (membrane) at a distance of 2–7 μm from the inner wall (holotype 4.5 μm, x = 4 μm); n = 6. Remarks. – The new species differs from C. kullingii by having processes piercing through the outer wall and being free in their terminal portion above this wall. The vesicle diameter overlaps in both species. However, in the description to emended species C. kullingii (Butterfield et al. 1994, p. 34), it is stated that the processes occur between the layers of the outer, multilayered wall, and depending on the preservation not all layers of the outer wall are present but processes may stretch above. The number of layers or membranes in the outer wall was recognized as 6 in the genus Cymatiosphaeroides (Knoll et al. 1991) and up to 12 in its emended type species C. kullingii (Buttefield et al. 1994). The outer wall layers, called alternatively envelopes, enveloping membranes or extracellular layers, are typically compressed or fused but may be separated and supported by processes (Butterfield et al. 1994, p. 34); thus, processes pierce all layers of the outer wall. These authors also recognized a greater variability of the species, both in a number of outer wall layers and dimensions of vesicle (40–400 μm; Butterfield et al. 1994). The multiple layers in the outer wall are not observed in the new species. Present record. – South China, Hubei Province, Yangtze Gorges area, northern and southern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran. Cymatiosphaeroides kullingii Knoll, 1984, emend. Butterfield, Knoll & Swett, 1994 Figure 42 1984 Cymatiosphaeroides kullingii n. sp.; Knoll, p. 153, fig. 9A–C.

FOSSILS AND STRATA

1985 cf. Cymatiosphaeroides kullingii Knoll, 1984; Vidal & Ford, pp. 359, 360, fig. 3B. 1989 Cymatiosphaeroides kullingii Knoll, 1984; Allison & Awramik, p. 287, fig. 11:1–3. 1991 Cymatiosphaeroides kullingii Knoll, 1984, emend.; Knoll, Swett & Mark, p. 557, fig. 4:4, 6. non 1993 Cymatiosphaeroides kullingii Knoll, 1984; Yuan, X., Wang, Q. & Zhang, Y., p. 415, pl. II, figs 2, 3. 1994 Cymatiosphaeroides kullingii Knoll, 1984 emend.; Butterfield, Knoll & Swett, pp. 34, 36, fig. 15A–E. 1995 Cymatiosphaeroides kullingii Knoll emend. Knoll, Swett & Mark, 1991; Zang, p. 163, fig. 24H–K. 2001 Cymatiosphaeroides kullingii Knoll, 1984; Anbarasu, p. 182, fig. 2a–f. 2005 Distosphaera australica sp. nov. Grey, pp. 246–250, figs 148–150. 2006 Cymatiosphaeroides kullingii Knoll emend Butterfield, Knoll & Swett, 1994; Veis, Vorobeva & Golubkova, pl. 3, fig. 1. non 2008 Cymatiosphaeroides kullingii (Knoll) Knoll et al., 1991; Xie, G., Zhou, C., McFadden, K.A., Xiao, S. & Yuan, X. p. 283, pl. 1, fig. 1. 2014 Cymatiosphaeroides kullingii Knoll, 1984; Singh & Sharma, p. 96, pl. IV, figs 9–11, pl. 5, figs 2, 5. 2014 Shuiyougousphaeridium echinulatum Yin & Gao, 1999; Singh & Sharma, p. 94, 96, pl. II, figs 1–3, pl. III, figs 1–9, pl. IV, fig. 4, 4a, pl. V, figs 1, 4. 2015 Cymatiosphaeroides kullingii Knoll, 1984, emend Knoll et al., 1991; Ye, Q., Tong, J., An, Z., Tian, L., Zhao, X. & Zhou, S. p. 48, pl. 1, figs 1, 2. Material. – Four relatively well‐preserved specimens. Description. – Vesicle small to medium‐sized, circular in outline, originally spheroidal, consisting of two walls: inner thick and bearing numerous tightly distributed, narrow, solid, rod‐like processes of equal length that is surrounded by the outer membraneous wall (or envelope). The outer wall is single‐layered and processes do not pierce this wall.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

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Fig. 42. A–D, Cymatiosphaeroides kullingii Knoll, 1984, emend. Butterfield, Knoll & Swett, 1994. A, IGCAGS‐DSY258, thin section DSY12.6‐7 (Y54/2, Z: 112 × 3.7). B, IGCAGS‐DSY163A, thin section DSY11.5‐14 (F35, Z: 93 × 20.5). C, IGCAGS‐DSY266B, thin section DSY12.6‐13 (V55/2, Z: 113.3 × 7). D, IGCAGS‐SXF088, thin section SXF2.5‐88 (R41/4, Z: 96 × 10.5). All specimens are entirely filled in by silica but preserve two walls and processes extending between them.

Dimensions. – Vesicle overall diameter 54–115 μm; processes length 4–8 μm or 5–11% of the vesicle diameter; process width ˂ 1 μm; processes spaced at 2–3 μm. Remarks. – The multilamellate structure of the outer wall has been diagnosed in the emendation to C. kullingii Knoll, 1984 (Knoll et al. 1991, p. 557), and subsequently as having up to 12 enveloping membranes (Butterfield et al. 1994, p. 34). The single or multiple layered envelope (= outer wall or enveloping membranes, or multiple layering of the envelope, or a number of enveloping layers) is supported by processes that also occur between multiple

layers, and it has been interpreted as showing variability of the species (Butterfield et al. 1994). The species has been studied in thin sections of diagenetic chert nodules and the appearance of multiple layers in the envelope surrounding the vesicle with processes may be diagenetically induced and a taphonomic artefact of mineral silica precipitation from a liquid solution forming thin outer layers. The appearance of multiple layers may equally be the result of sectioning of a folded single envelope, and there is no clear appearance of numerous extracellular layers in any illustrated specimen from the Svanbergfjellet Formation, the Draken Conglomerate

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Formation or the Hunnberg Formation (all formations in Svalbard) in occurrences cited above. In the present material, the outer wall seems to be membranous and single‐layered. Only three specimens extracted from the rock matrix of the Kwagunt Formation (Chuar Group of the Grand Canyon, Arizona) that may belong to the species but identified as cf. C. kullingii Knoll, 1984, show a single membrane (Vidal & Ford 1985, fig. 3B). Similarly, C. kullingii observed in thin section of phosphorite in the Doushantuo Formation of the Yangtze Gorges area shows a single‐layered, thin, outer wall (Ye et al. 2015). The same feature is seen in specimens of C. kullingii from thin sections of chert nodules of the Late Palaeoproterozoic to Mesoproterozoic Chitrakut Formation, Vindhyan Supergroup, and the Mesoproterozoic Chitrakoot Formation, Semri Group in Central India (Anbarasu et al. 2001; Singh & Sharma 2014). Additionally, the specimens described as Shuiyousphaeridium echinulatum (Singh & Sharma 2014) and bearing numerous tightly distributed, narrow, solid, rod‐like processes of equal length and surrounded by single membraneous envelope, are considered herein conspecific with C. kullingii. Other species of Cymatiosphaeroides, C. yinii Yuan and Hofmann, 1998, preserved in phosphorite and observed in thin sections, shows a single, thin outer wall. The overall vesicle diameter is variable and substantial in a range of 40–400 μm (Butterfield et al. 1994; Anbarasu et al. 2001; Singh & Sharma 2014). Accepting the synonymous species from India, and re‐evaluating the age of the successions from Canada (the Tindir Group is transferred to the Fifteenmile Group and Tonian in age; Kaufman et al. 1992; Macdonald et al. 2011) and Svalbard (the Svanbergfjellet Formation) as Tonian, the species stratigraphic range is late Palaeoproterozoic–Mesoproterozoic, and certainly Tonian to Ediacaran. Present record. – Yangtze Gorges area, Dishuiyan section, Doushantuo Formation, member III, and southern Xiaofenghe section, Doushantuo Formation, member II, Ediacaran. Occurrence and stratigraphic range. – Norway, Svalbard Archipelago, Draken, Svanbergfjellet, and Hunnberg Formations, Neoproterozoic (Knoll 1984; Knoll et al. 1991; Butterfield et al. 1994). Canada, upper Tindir Creek, upper Tindir Group, Unit 5, the latest Proterozoic (Allison & Awramik 1989), currently the succession referred to the Fifteenmile Group, and Tonian in age (Macdonald et al. 2011). USA, northern Arizona, Chuar Group, Kwagunt

FOSSILS AND STRATA

Formation, the Awatubi Member, the late Proterozoic (Vidal & Ford 1985), currently referred to the Tonian age (Dehler et al. 2001). South Australia, Officer Basin, Neoproterozoic (Zang 1995), and Observatory Hill 1 borehole, in the interval of 232.2–233.0 m, Munta 1 borehole, at a depth of 1224.6 m, the Tanana Formation, Ediacaran (Grey 2005). Russia, East European Platform, Vychegda Formation, Lower Vendian (Veis et al. 2006). Central India, Chitrakoot area, Semri Group, Chitrakoot Formation, Mesoproterozoic (Anbarasu et al. 2001), Vindhyan Supergroup, Chitrakut Formation, the late Palaeoproterozoic–early Mesoproterozoic (Singh & Sharma 2014). South China, Hubei Province, Zhangcunping area, ZK407 borehole, Doushantuo Formation, Ediacaran (Ye et al. 2015). Genus Dicrospinasphaera Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended Type species. – Dicrospinasphaera zhangii Yuan & Hofmann, 1998, emend. Yin et al., 2011b, emended; from South China, Guizhou Province, Weng'an phosphate Mine, Doushantuo Formation, Upper Sinian (= Ediacaran; Yuan & Hofmann, 1998; Yin et al. 2011b). Other species. – Dicrospinasphaera improcera n. sp.; D. virgata Grey, 2005. Emended diagnosis. – Spheroidal vesicle having thick, inner wall bearing numerous heteromorphic processes, branching and simple, and surrounded by thin membraneous outer wall that is supported by process tips. Processes are bi‐ or trifurcating at various process portions or are simply tubular with widened or blunt tips; they may have small conical bases or arise straight from vesicle wall. Processes are hollow inside and freely communicate with the vesicle cavity. The external membraneous wall surrounding the vesicle and processes may not always be preserved. Remarks. – The proposed emendation differs from the original diagnosis of the genus and type species D. zhangii by Yuan & Hofmann (1998) and the emendation by Yin et al. (2011b) by recognizing that the processes are hollow instead of being solid. This is based on new observations of processes in D. zhangii and by comparison with other species of the genus preserved at various state of preservation in diagenetically mineralized specimens and those preserved organically in shale. The presence of an external membraneous wall surrounding the vesicle and processes is included in agreement with the previous

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

emendation of the genus and its type species by Yin et al. (2011b). The vesicle diameter about 60 μm in the original diagnosis by Yuan & Hofmann (1998) is extended in subsequent studies and not restricted in the emendations. Dicrospinasphaera improcera n. sp. Figure 43 Holotype. – Specimen IGCAGS‐NP1‐159, thin section NP81120‐6T, V37/1; illustrated in Figure 43E. 2008 Cymatiosphaeroides kullingii (Knoll) Knoll et al., 1991; Xie, Zhou, McFadden, Xiao, & Yuan, p. 283, pl. 1, fig. 1. Derivation of name. – From Latin improcerus – small, with reference to the size of processes in relation to the vesicle diameter. Locus typicus. – South China, Hubei Province, Yangtze Gorges area, Niuping section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at a level of 67 m in the Niuping section. Material. – 24 well‐preserved specimens. Diagnosis. – Vesicle circular in outline, probably originally spheroidal, having thick, dense inner wall bearing numerous, closely distributed short processes of equal length and surrounded by the thin, membraneous outer wall. Processes are heteromorphic, branching terminally or occasionally from the bases into fork‐shape terminations, or are simple with widened or blunt tips. Processes arise straight from the vesicle inner wall, are tubular in stem portion and appear to be hollow. Dimensions. – Vesicle diameter 42–65 μm (holotype 46 μm, x = 50 μm, δ = 6.5 μm); process length 2– 3 μm (holotype 2 μm, x = 2.5 μm, δ = 0.5 μm) or 3.8–6% of the vesicle diameter (holotype 4.4%, x = 4.7% of the diameter, δ = 0.7%); width of process bases ˂ 1 μm; processes spaced at a distance of 1– 3 μm; n = 24. Remarks. – The specimen described as Cymatiosphaeroides kullingii by Xie et al. (2008) is considered conspecific with our new species. The new species is distinguished from other species of the genus by having processes that are very

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short in relation to the vesicle diameter, and more uniform in their shape as well as more abundant. The vesicle diameter is however similar to D. zhangii, which is in a range of 60–80 μm (Yuan & Hofmann 1989; Xiao et al. 2014a), whereas D. virgata diameter is 160–330 μm and of a different size cluster (Grey 2005). The process length of 2–3 μm in the new species is well below the range of 6–15 μm in D. zhangii (Fig. 44), and obviously the length of processes 20– 60 μm in D. virgata. Whether the processes are solid or hollow is difficult to determine because of the mode of preservation in chert and diagenetic permineralization resulting in impregnation by silica and the filling in of any void in the vesicle by mineral or organic fraction or particles. Processes appear dark and solid but several in the same specimen are light and tubular (Figure 43B, D), and hollow inside. The heteromorphic processes, not only in the shape of processes but also being hollow and solid have been diagnosed in D. virgata in specimens extracted from the rock matrix (Grey 2005). These specimens of D. virgata seem to have tubular processes in stem portion below the branches and feely communicating with the vesicle cavity. The variety of processes (opaque and appearing to be solid or partially solid in some segments of hollow processes) in a single specimen is a taphonomic feature reflecting the thickness of the process wall or their width becoming opaque when compressed. In silicified or phosphatized specimens of Dicrospinasphaera species observed in the Doushantuo Formation (Yuan & Hofmann 1998; Yuan et al. 2002; Xiao 2004; Xiao et al. 2014a; Yin et al. 2007a; Yin et al. 2011b; Ouyang et al. 2015; and herein), the processes are predominantly dark and apparently solid but it is considered to be a taphonomic and not morphologic feature. Phosphatized specimens of D. virgata in the Doushantuo Formation are opaque and ‘solid’ in appearance (Xiao et al. 2014a, fig. 9:1–9), but without diagenetic mineralization are clearly hollow (see Grey 2005, fig. 141A, B) or partly hollow (Grey 2005, fig. 141D, E). Similar taphonomic alteration is observed in phosphatized specimens of Cavaspina basiconica from the Doushantuo Formation, which are opaque and look like being solid (Xiao et al. 2014a, fig. 8:5– 8), but when observed in organically preserved specimens extracted from shales are hollow (Moczydłowska et al. 1993; Moczydłowska 2005). These examples prove the taphonomic changes due to permineralization may be easily misinterpreted as morphologic features. Specimens attributed to D. virgata by Sergeev et al. (2011) and D. sp. by Vorobeva et al. (2008), which have thick and hollow processes, have been

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Fig. 43. A–F, Dicrospinasphaera improcera n. sp. A, IGCAGS‐NTC1.2‐3‐7, thin section NTC1.2‐3 (Q46/3, N: 44.6 × 101.8). B, IGCAGS‐ XFHD‐27(5)‐2‐8, thin section XFHD‐27(5)‐2 (Q23/1, N: 22.5 × 101). C, IGCAGS‐NP1‐101, thin section NP15‐2‐3 (G44, Z: 103 × 20). D, IGCAGS‐NP1‐158, thin section NP81120‐6T (V39/3, Z: 97.5 × 23.5). E, holotype, IGCAGS‐NP1‐159, thin section NP81120‐6T (V37/1, Z: 98 × 10.8). F, IGCAGS‐D2XFH647, thin section XFH0946‐1‐172 (O50, N: 48.4 × 103.2). Arrows in all specimens point to bifurcating processes. Specimen B demonstrates the compressed vesicle while the others seem to be three‐dimensionally preserved.

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Ediacaran microfossils from the Doushantuo Formation

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Fig. 44. Statistical comparison of vesicle and processes size classes of Dicrospinasphaera improcera n. sp. and Dicrospinasphaera zhangii Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended.

suggested by Xiao et al. (2014a) to belong to Variomargosphaeridium or Multifronsphaeridium. These specimens show processes of different shape and pattern of branching and are excluded from Dicrospinasphaera. Present record. – Yangtze Gorges area, Jiulongwan, Chenjiayuanzi, Nantuocun, Niuping, northern and southern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran. Occurrence and stratigraphic range. – South China, Hubei Province, Yangtze Gorges area, Jiulongwan section, Doushantuo Formation, member II, Ediacaran (Xie et al. 2008). Dicrospinasphaera zhangii Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended Figure 45 1998 Dicrospinasphaera zhangii gen. et sp. nov.; Yuan & Hofmann, pp. 199, 202, fig. 7A, B. 2002 Dicrospinasphaera zhangii Yuan & Hofmann, 1998; Yuan, Xiao, Yin, Knoll, Zhou & Mu, p. 82, fig. 114. 2004 Dicrospinasphaera zhangii Yuan & Hofmann, 1998; Xiao, p. 399, fig. 3:10, 11. 2007 Dicrospinasphaera zhangii Yuan & Hofmann, 1998; Yin, C., Liu, Y, Gao, L., Wang, Z., Tang, F. & Liu, P., pl. 15, figs 5–9. 2011 Dicrospinasphaera zhangii (Yuan & Hofmann, 1998) emend.; Yin, L., Wang, D., Yuan, X. & Zhou, C. p. 287, fig. 4H, K.

2014 Dicrospinasphaera zhangii Yuan & Hofmann, 1998; Xiao, S., Zhou, C., Liu, P., Wang, D. & Yuan, X., 2014a, p. 20, fig. 10:1–6. 2015 Dicrospinasphaera zhangii Yuan & Hofmann, 1998; Ouyang, Zhou, Guan & Wan, p. 216, pl. I, figs 9, 10. Material. – 31 very well‐preserved specimens. Emended diagnosis. – Vesicle circular in outline, originally spheroidal, having thick, firm inner wall bearing numerous and evenly distributed processes of approximately equal length and surrounded by an outer membraneous wall supported by processes. Processes are heteromorphic, predominantly branching into bifurcate and occasionally trifurcate terminations and simple with widened tips. Processes are tubular in stem portions and arise straight from vesicle inner wall or have small conical bases. Processes are hollow, and those with conical bases show free communication with the vesicle cavity. The outer membraneous wall not always preserved. Dimensions. – Vesicle diameter 50–75 μm (x = 64 μm, δ = 8.4 μm); process length 6–13 μm (x = 9 μm, δ = 2 μm) or 10.3–19% of the vesicle diameter (x = 13.8%, δ = 2.5%); width of process bases ~1 μm; processes spaced at a distance of 3–8 μm; n = 31. Remarks. – The appearance of processes as solid in D. zhangii has been commented upon as uncertain by Xiao et al. (2014a). We consider the opaqueness of processes, and inference of being solid, to result from permineralization and diagenetic alteration, and observe processes that are light in colour, transparent and hollow inside, and have bases freely communicating with the vesicle cavity (Fig. 45B, D, F). We propose the new

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Fig. 45. A–F, Dicrospinasphaera zhangii Yuan & Hofmann, 1998, emend. Yin, Wang, Yuan & Zhou, 2011, emended. A, IGCAGS‐ JQN022, thin section JQN‐1‐11 (M44, Z: 103 × 14.6). B, IGCAGS‐JQN027, thin section JQN‐1‐13 (J43/4, Z: 102.4 × 17.3). C, IGCAGS‐ JQN081, thin section JQN‐1‐13 (R43, Z: 101.8 × 10). D, IGCAGS‐JQN169, thin section 11922‐2‐5 (H45, N: 43.4 × 108.9). E, IGCAGS‐ JQN264, thin section 11922‐4‐15 (U37/1, N: 36 × 97.3). F, IGCAGS‐JQN198, thin section 11922‐3‐3 (L44/1, N: 42.9 × 106). Specimens with fragmentarily preserved organic matter within the vesicle cavity (A, B, D, F) and entirely filled in by silica (C, E).

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

emendation to the diagnosis of the genus, of which D. zhangii is the type species, to recognize that the processes are hollow and heteromorphic in shape. We include the outer membraneous wall that surrounds the vesicle and is supported by process terminations into the diagnosis following the previous emendation by Yin et al. (2011b). Although rarely preserved, this feature is significant morphologically and for the inference of ontogenetic development of the species indicating the cyst stage in a complex life cycle of microorganism. There are several Ediacaran taxa, as well as of other ages, that show such a feature allowing reconstruction of reproductive cycle and bearing comparisons upon biological affinities of microfossils (Moczydłowska 2011, 2015; Agić et al. 2015). The presence of an outer membraneous wall in D. zhangii adds this feature to the known record among other species and enhances its meaning for both taxonomic descriptions and biological affinities hypotheses. Present record. – Yangtze Gorges area, southern Xiaofenghe, Jiulongwan and Jiuqunao sections, Doushantuo Formation, member II, Ediacaran. Occurrence and stratigraphic range. – South China, Guizhou Province, Weng'an area, unit 4A, Doushantuo Formation, Ediacaran (Yuan & Hofmann 1998; Yuan et al. 2002; Yin et al., 2007a; Yin et al. 2011b; Xiao et al. 2014a); Hubei Province, Yangtze Gorges area, Nantuocun section, upper Doushantuo Formation, upper chert (Xiao 2004); Qinglinkou and Jinguadun sections, Doushantuo Formation, member II, Ediacaran (Ouyang et al. 2015). Genus Distosphaera Zhang, Yin, Xiao & Knoll, 1998, emended Type species. – Distosphaera speciosa Zhang, Yin, Xiao and Knoll, 1998, emended; from South China, Guizhou Province, Weng'an‐Fuquan phosphate mine, Doushantuo Formation, Neoproterozoic (Zhang et al. 1998b; = Ediacaran). Other species. – Non Distosphaera australica Grey, 2005 (transferred herein to Cymatiosphaeroides kullingii); Distosphaera? corniculata n. sp. Emended diagnosis. – Vesicle circular in outline, originally spheroidal, consisting of two walls: thick, firm inner wall bearing numerous, narrow cylindrical and hollow processes, which support thin, membraneous outer wall bearing less numerous and wide conical processes with round or sharp‐pointed tips. Both types of processes are evenly distributed on respective

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walls but are not aligned with each other. Processes on inner wall arise straight from wall, are hollow though very narrow, freely communicate with the vesicle cavity and their blunt tips support outer wall. Processes on outer membraneous wall are formed by the extension of this wall and bulge out of it, and their interior is connected with the void between both walls. Remarks. – The emendation to genus diagnosis is as for the type species D. speciosa Zhang, Yin, Xiao & Knoll, 1998, emended. The processes on the inner wall were diagnosed as slender solid, but in the present material (Fig. 45B) they are visible to be narrow cylindrical and hollow. The species D. australica Grey, 2005, has been diagnosed as having solid and narrowly conical processes evenly distributed on the vesicle wall and supporting a thin undulose outer membrane (Grey 2005). In this species, there is one type of processes and the outer membrane has no conical hollow processes as in the genus Distosphaera (Zhang et al. 1998b). We consider D. australica as belonging to Cymatiosphaeroides kullingii. Grey (2005) commented that rare specimens of D. australica possess one or two tapering, hollow, thin processes arising from the outer membrane but this is not clearly documented. It may be a taphonomic feature, or if the processes are present, they contrast with those well distinguished from the outer wall (= outer membrane) and wide conical processes in Distosphaera. Additionally, the species australica may be another species of Cymatiosphaeroides (C. australicus, comb. nov.) having wider and conical solid processes. Otherwise, if the difference in the shape of processes is difficult to recognize from those solid, narrow and rod‐like processes in Cymatiosphaeroides kullingii, the species australica may be synonymous. Distosphaera? corniculata n. sp. Figure 46 Holotype. – Specimen IGCAGS‐JQN231, thin section 11922‐3‐11, Y41/2; illustrated in Figure 46A–E. 1998 Meghystrichosphaeridium sp.; Yuan & Hoffman, p. 203, fig. 11A, B. 2014 Mengeosphaera sp.; Xiao, X., Zhou, C., Liu, P., Wang, D. & Yuan, X., 2014a, p. 43, fig. 28:1–8. Derivation of name. – From Latin cornu – horn, horn‐shaped, referring to the overall shape of processes with internal core.

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Fig. 46. A–G, Distosphaera? corniculata n. sp. A–E, holotype, IGCAGS‐JQN231, thin section 11922‐3‐11 (Y41/2, N: 40.6 × 93.6); B–E, enlarged fragments shown by arrows in A, blue arrow refers to B, red to C, white to D and yellow to E. F–G, IGCAGS‐SXF094, thin section SXF2.5‐106 (L47, Z: 101 × 17); G, enlarged fragment shown by arrow in F, and arrows point to the inner core of processes.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

Locus typicus. – Yangtze Gorges area, Jiuqunao section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at the level of 31 m. Material. – Two specimens from member II of the Doushantuo Formation. Diagnosis. – Vesicle thick‐walled, medium‐ to large‐ sized, spheroidal, bearing abundant and evenly distributed narrow conical processes, which are gradually tapering from bases to sharp‐pointed tips. Processes are enveloped in terminal portions by thin, translucent membrane, which is supported by process tips and is concave between processes forming wavy outline. Processes are thin‐walled and have inner core of the same shape as process but thick and opaque. They are hollow and freely communicate with vesicle cavity. Dimensions. – Vesical diameter 196–308 μm; process length 32–37 μm; width of process bases 6– 17 μm; width of inner core 1–3 μm. Remarks. – Processes are hollow but their communication with vesicle cavity is not clearly seen in the present material although seems to be free. Processes are regular in shape, conical, relatively short in relation to vesicle diameter, and not biform, thus not pertaining to Mengeosphaera, as preliminarily attributed synonymous indet. species (Xiao et al. 2014a). Similarity of the overall process shape to this of M. chadianensis is observed but the presence of the outer membrane is a distinct feature together with the inner core of the processes. The uncertain attribution to the genus Distosphaera is due to the presence of one type of processes that are located on the inner, thick wall of the vesicle and support the outer membraneous wall. Process inner core (Fig. 46B, D) seems to be extended from the thick vesicle wall, and it may appear that processes are formed by two elements: thick, opaque inner core and parallel thin wall that extends to the tip and supports the outer membrane. The outer membrane is stretched around the entire vesicle and processes with portions hanging down between the processes. Present record. – South China, Hubei Province, Yangtze Gorges area, Jiuqunao and southern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran.

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Occurrence and stratigraphic range. – South China, Guizhou Province, Weng'an area, Upper Doushantuo Formation, Ediacaran (Yuan & Hoffman 1998; Xiao et al. 2014a). Distosphaera speciosa Zhang, Yin, Xiao & Knoll, 1998, emended Figure 47 1993 Cymatiosphaeroides kullingii Knoll, 1984; Yuan, X., Wang, Q. & Zhang, Y., p. 415, pl. II, figs 2, 3. 1998 Distosphaera speciosa new species; Zhang, Y., Yin, L., Xiao, S. & Knoll, A.H., 1998b, pp. 24, 26, fig. 6:5, 6. 2014 Distosphaera speciosa; Liu, P., Chen, S., Zhu, M., Li, M., Yin, C. & Shang, X., 2014a, fig. 7A. Material. – 15 very well‐preserved specimens. Emended diagnosis. – Double‐walled vesicle, circular in outline, originally spheroidal, consisting of thick inner wall and thin, membraneous outer wall. The inner wall bears numerous, narrow, cylindrical and hollow processes, which arise straight from wall and have blunt or slightly widened tips supporting outer wall. These processes freely communicate with vesicle cavity and irregularly distributed. Outer membraneous wall bears wide, conical and hollow processes with rounded or tapering tips, which extend from outer wall and are freely connected with void between both walls. Both types of processes are not aligned with one another. Dimensions. – Vesicle diameter of inner wall 36– 72 μm (x = 52 μm, δ = 10 μm, n = 15); distance between two walls is equal to length of cylindrical processes 2–8 μm (x = 4.3 μm, δ = 1.6 μm, n = 15); width of cylindrical processes ˂ 1 μm and they are spaced at 1–8 μm; conical process length 2–8 μm (x = 4 μm, δ = 1 μm, n = 49); width of conical process bases 3–7 μm (x = 5 μm, δ = 1 μm, n = 49) and they are spaced at 1–12 μm. Remarks. – Cylindrical processes on the inner wall may occasionally divide or be V‐shaped (Fig. 47B, F), but they are predominantly homomorphic and although narrow they are hollow inside and freely communicate with the vesicle cavity (Fig. 47B, D). In the original diagnosis of the type species and new genus, which was based on observations of only two

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Fig. 47. A–F, Distosphaera speciosa Zhang, Yin, Xiao & Knoll, 1998, emended. A–B, IGCAGS‐NXF010, thin section NXF30.7‐4 (T42, Z: 96 × 9); B, enlarged fragment shown by arrow in A. C, IGCAGS‐D2XFH685, thin section XFH0946‐1‐188 (V34, N: 33.6 × 96.2). D, IGCAGS‐WF084, thin section WFG22.4‐20 (J48/4, Z: 106 × 17.8). E, IGCAGS‐D2XFH688, thin section XFH0946‐1‐194 (O29/3, N: 28.2 × 102.6). F, IGCAGS‐LHW076, thin section LHW‐0.35‐13 (P46/4, Z: 104.1 × 11.8).

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

specimens, the processes were characterized as solid (Zhang et al. 1998) because of their opaque appearance as was also the vesicle cavity. The processes on the outer wall were diagnosed as sharp‐pointed but the type material shows both rounded and sharp‐pointed tips of processes. In the present record (n = 15), processes on outer wall are mostly rounded (Fig. 47A, D, F) but can also taper at their terminations (Fig. 47F). Present record. – Yangtze Gorges area, Chenjiayuanzi, Jiulongwan, Nantuocun, Niuping, Jiuqunao, Wangfenggang, northern and southern Xiaofenghe sections, Doushantuo Formation, member II, and the Liuhuiwan section, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – South China, Guizhou Province, Weng'an area, Doushantuo Formation, Ediacaran (Zhang et al. 1998b); Hubei Province, Yangtze Gorges area, Chenjiayuanzi section, Doushantuo Formation, member II, Ediacaran (Liu et al. 2014a). Genus Eotylotopalla Yin, 1987 Type species. – Eotylotopalla delicata Yin, 1987; from South China, Hubei Province, the Yangtze Gorge area, Upper Doushantuo Formation (Yin 1987). Other species. – E. dactylos Zhang, Yin, Xiao & Knoll, 1998; E. quadrata n. sp.; E. strobilata (Faizullin 1998) Sergeev, Knoll & Vorobeva, 2011. Remarks. – All species recognized have overlapping size ranges and their ranges are substantially extended through the subsequent studies (current range of diameter 35–230 μm). The shape of their processes has several transitional morphotypes. This may reflect morphologic plasticity and infraspecific and/or taphonomic variants. The processes of D. delicata and D. dactylos show gradational change of shape and dimensions. Eotylotopalla dactylos Zhang, Y., Yin L., Xiao & Knoll, 1998 Figure 48 1998 Eotylotopalla dactylos new species; Zhang, Y., Yin L., Xiao, S. & Knoll, A.H., 1998b, p. 26, fig. 7:8, 9. 2002 Eotylotopalla dactylos Zhang et al., 1998; Yuan, X., Xiao, S., Yin, L., Knoll, A.H., Zhou, C. & Mu, X. p. 72, fig. 92.

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2007 Eotylotopalla dactylos Zhang et al., 1998; Zhou, C., Xie, G., McFadden, K., Xiao, S. & Yuan, X., p. 245, fig. 4F. 2011 Eotylotopalla dactylos Zhang et al., 1998; Yin, L., Wang, D., Yuan, X. & Zhou, C., p. 285, fig. 3G. 2014 Eotylotopalla dactylos Zhang, Yin, Xiao & Knoll, 1998b; Xiao, Zhou, Liu, Wang & Yuan, 2014a, p. 20, fig. 11:1–3. 2014 Eotylotopalla dactylos Zhang, Yin, Xiao & Knoll, 1998b; Liu, Xiao, Yin, Chen, Zhou & Li, 2014b, pp. 50, 55, fig. 31:1–9. Material. – 18 very well‐preserved specimens. Description. – Vesicle spheroidal, bearing not numerous processes of regular shape and dimensions that are evenly distributed. Processes are digitate in shape having round terminations and slightly widened bases continuously extending from the vesicle surface. Processes are hollow and freely communicate with vesicle cavity. Dimensions. – Vesicle diameter 34–102 μm (x = 51, δ = 19.5 μm, n = 18); process length 6–24 μm (x = 11.5 μm, δ = 4.3 μm, n = 59) or 12.2–30.8% of the vesicle diameter (x = 22.5%, δ = 3.9%, n = 59) and width 6–22 μm (x = 10.5 μm, δ = 4 μm, n = 59). Processes spaced at a distance of 1–6 μm; number of processes observed on vesicle outline 8–13 (x =10). Remarks. – The species size range compiled from known occurrences is 35–200 μm in vesicle diameter, 6–30 μm in process length and 5–22 μm in width of process bases. However, regardless of the dimensions, the specimens are very regular in their overall shape and the proportions of vesicle diameter to process length are similar. Present record. – South China, Hubei Province, Yangtze Gorges area, Wangfenggang and Chenjiayuanzi sections, Doushantuo Formation, member II, and the Chenjiayuanzi and Dishuiyan sections, Doushantuo Formation, member III; Ediacaran. Occurrence and stratigraphic range. – South China, Hubei Province, Yangtze Gorges area, Xiaofenghe section, Doushantuo Formation, upper Doushantuo chert (Zhang et al. 1998b; Yuan et al. 2002), Tianjiayuanzi section, Doushantuo Formation, Member III (Zhou et al. 2007), and Wangfenggang, Xiaofenghe and Niuping sections, Doushantuo Formation, member III (Liu et al. 2014b); Yangtze Gorges area, lower

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Fig. 48. A–D, Eotylotopalla dactylos Zhang, Yin L., Xiao & Knoll, 1998. A, IGCAGS‐CJ283A, thin section CJ137.4‐3 (G59/2, Z:116.4 × 21). B, IGCAGS‐DSY144, thin section DSY11.5‐9 (G39, Z: 97.3 × 20.5). C, IGCAGS‐DSY182, thin section DSY11.5‐19 (J37, N: 35.7 × 107.8). D, IGCAGS‐CJ323A, thin section CJ141‐2 (M38, Z: 96 × 10.5).

Doushantuo Formation, Ediacaran (Yin et al. 2011b); South China, Weng'an locality, unit 4A, Doushantuo Formation (Xiao et al. 2014a). Eotylotopalla delicata Yin, L., 1987 Figure 49 2006 Vesicles with large hemispherical processes; Veis, Vorobeva & Golubkova, pl. 4, figs 13, 24. 2006 Pulvinosphaeridium aff. P. antiquum Paskeviciene; Veis, Vorobeva & Golubkova, pl. 4, fig. 22.

2007 Vesicles with large hemispherical processes; Vorobeva, Sergeev & Knoll, pl. 1, fig. 1. 2009 unnamed form with hemispherical processes; Vorobeva, Sergeev & Knoll, 2009b, fig. 4 g. 2009 Timanisphaera apophysa n. sp.; Vorobeva, Sergeev & Knoll, 2009a, p. 183, fig. 12:1–7, 9, 10. 2014 Eotylotopalla delicata Yin, 1987; Liu, Xiao, Yin, Chen, Zhou & Li, 2014b, pp. 57, 61 (cum syn.), fig. 32:1–11.

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Ediacaran microfossils from the Doushantuo Formation

97

Fig. 49. A–B, Eotylotopalla delicata Yin L., 1987. A, IGCAGS‐DSY034A, thin section DSY4.5‐12 (N52/1, Z: 109.3 × 14.8). B, IGCAGS‐ DSY324, thin section DSY22.45‐12 (G13, Z: 72.2 × 19.5).

Material. – Five well‐preserved specimens. Description. – Vesicle spheroidal with thick and firm wall, bearing numerous bulbous processes that extend continuously from the vesicle wall and obscure its outline. Processes are hemispherical to wide conical in shape, hollow inside and freely communicate with vesicle cavity. Processes are large in comparison with vesicle diameter. Dimensions. – Vesical diameter 40–65 μm; process length 10–17 μm; width of process bases 11–19 μm. Present record. – South China, Hubei Province, Yangtze Gorges area, Dishuiyan, Jiuqunao and Chenjiayuanzi sections, Doushantuo Formation, member II, and the Dishuiyan section, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – South China, Hubei Province, Yangtze Gorges area, Liantuo section, upper Doushantuo Formation, latest Precambrian (Yin 1987, = Ediacaran), Xiaofenghe section, upper Doushantuo Formation, terminal Proterozoic (Zhang et al. 1998b, = Ediacaran), Wangfenggang and Xiaofenghe sections, Doushantuo Formation, member III, Ediacaran (Liu et al. 2013, 2014b); Changyang area, Gaojiayan section, Doushantuo Formation, Sinian (Yin & Liu 1988; Yin & Gao 1995; = Ediacaran), Wangfenggang section, Doushantuo Formation, Sinian (Yin et al. 2007a, 2011a; = Ediacaran); Guizhou Province, Weng'an area, Doushantuo Formation, Ediacaran (Yin et al. 2011b). The northeastern margin of

the East European Platform, Keltminskaya 1 borehole, Vychegda Formation, Neoproterozoic (Veis et al. 2006; Vorobeva et al. 2007, 2009a, 2009b). Eotylotopalla quadrata n. sp. Figure 50 Holotype. – Specimen IGCAGS‐D2XFH048, thin section XFH81120‐2X‐6, T45/4; illustrated in Figure 50A. Derivation of name. – From Latin quadratus – square, referring to the overall shape of processes. Locus typicus. – Yangtze Gorges area, northern Xiaofenghe section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at a level of 113 m of northern Xiaofenghe section. Material. – Five well‐preserved specimens. Diagnosis. – Species of Eotylotopalla with small‐ to medium‐sized vesicle bearing relatively abundant and large processes, which are well differentiated and spaced, cubical or square‐shaped in side view. Processes are hollow and freely communicating with the vesicle cavity. Dimensions. – Holotype: vesicle diameter 47 μm; process length 7 μm and width 5–8 μm; processes spaced at 1–5 μm. Other specimens: vesicle diameter

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Fig. 50. A–F, Eotylotopalla quadrata n. sp. A, holotype, IGCAGS‐D2XFH048, thin section XFH81120‐2X‐6 (T45/4, N: 44.4 × 97.8). B, IGCAGS‐D2XFH071, thin section XFH81120‐2X‐29 (L44/4, N: 43.2 × 105.8). C, IGCAGS‐NP1‐203, thin section NP14‐2‐6 (Y52/3, N: 50.4 × 92.6). D, IGCAGS‐D2XFH699, thin section XFH0946‐1‐207 (T31, N: 30.7 × 98.2). E–F, IGCAGS‐D2XFH230, thin section XFH0946‐1‐13 (E54, N: 52.5 × 111.7), specimen shown at different focal levels.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

64–107 μm; process length 5–13 μm (x = 6.8 μm, δ = 3.2 μm, n = 52) or 5.8–14% of the vesicle diameter (x = 9.3%, δ = 2.5%, n = 52) and width 4– 12 μm (x = 6.4 μm, δ = 2.1 μm, n = 52). Processes spaced at a distance of 1–5 μm. Remarks. – The new species ratio of process length to vesicle diameter is higher than in E. strabilata, and process shape differs from hemispherical small processes in the latter species. E. quadrata n. sp. differs from E. delicata Yin, 1987 by the shape of processes, being bulbous in the latter species, and from E. dactylos Zhang et al. 1998 in having more cylindrical and elongate processes. The spaced and robust processes in the new species may resemble those in Bullatosphaera velata Vorobeva et al. 2009a. However, the square appearance of processes in a side view of the new species differs from spheroidal processes in Bullatosphaera velata Vorobeva et al. 2009a, as well as the overall diameter of B. velata vesicle is three‐ to fourfold larger (Vorobeva et al. 2009a). Present record. – South China, Hubei Province, Niuping and northern Xiaofenghe sections, Doushantuo Formation, member II, Ediacaran. Eotylotopalla strobilata (Faizullin, 1998) Sergeev, Knoll & Vorobeva, 2011 Figure 51 1998 Lophosphaeridium strobilatum sp. nov.; Faizullin, pp. 331, 332, pl. 1, figs 4, 5. 2004 Lophodiacrodium sp.; Nagovitsin, Faizullin & Yakshin, p. 14, pl. 1, fig. 4. pro parte 2006 Bavlinella faveolata Schepeleva, 1962; Vorobeva, Sergeev & Semikhatov, fig. 2w. 2009 Eotylotopalla minorosphaera new species; Vorobeva, Sergeev & Knoll, 2009a, p. 178, fig. 9:11a, b. 2011 Eotylotopalla strobilata (Faizullin, 1998) new combination; Sergeev, Knoll & Vorobeva, p. 1003, fig. 9:1, 4. 2014 Eotylotopalla strobilata (Faizullin, 1998) Sergeev, Knoll & Vorobeva, 2009; Liu, P., Chen, S., Zhu, M., Li, M., Yin, C. & Shang, X. 2014a, fig. 9C.

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Material. – Five relatively well‐preserved specimens. Description. – Vesicle circular to oval in outline, originally spheroidal, bearing abundant, closely distributed but separated from each other, hemispheroidal processes of equal dimensions or slightly elongated. Processes are hollow and freely communicate with the vesicle cavity. Dimensions. – Vesicle diameter 45–231 μm; process length 3–8 μm; width of process bases 4–5 μm. Remarks. – Present specimens are much larger in diameter than recorded previously in a range of 65–85 μm (Sergeev et al. 2011), but the overall morphology and uniform shape processes are consistent features in all illustrated specimens of the species. Present record. – South China, Hubei Province, Yangtze Gorges area, Chenjiayuanzi, Niuping and Liuhuiwan sections, Doushantuo Formation, member III, Ediacaran. Occurrence and stratigraphic range. – Russia, East European Platform, Timan Uplift, Vychegda Formation, Ediacaran (Vorobeva et al. 2006, 2009a). Siberia, Baikal‐Patom Uplift, Ura Formation, Ediacaran (Faizullin 1998; Nagovitsin et al. 2004; Sergeev et al. 2011). South China, Hubei Province, Yangtze Gorges area, Chenjiayuanzi section, Doushantuo Formation, member III, Ediacaran (Liu et al. 2014a). Genus Ericiasphaera Vidal, 1990, emend. Grey, 2005 Type species. – Ericiasphaera spjeldnaesii Vidal, 1990; from southern Norway, Hedmark Basin, at locality Hjellund, Biskopås Conglomerate, Upper Proterozoic (Vidal 1990; = Tonian age). Other species. – E. adspersa Grey, 2005; E. crispa Xiao, Zhou, Liu, Wang & Yuan, 2014; E. densispina Liu, Xiao, Yin, Chen, Zhou & Li, 2014; E. fibrilla n. sp.; E. magna (Zhang, 1984) Zhang, Yin L, Xiao & Knoll, 1998; non E. polystacha Grey, 2005; E. rigida Zhang, Yin L, Xiao & Knoll, 1998; E. sparsa Zhang, Yin L, Xiao & Knoll, 1998. Remarks. – The species E. polystacha Grey, 2005 shows narrowly conical processes that are hollow inside and freely communicate with the vesicle

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Fig. 51. A–G, Eotylotopalla strobilata (Faizullin, 1998) Sergeev, Knoll & Vorobeva, 2011. A, IGCAGS‐CJ445, thin section CJ137‐8 (K25/1, N: 24.3 × 107.1). B, IGCAGS‐LHW176, thin section LHW6.7‐15 (H29/2, Z: 87.7 × 19). C–D, IGCAGS‐NP3‐629, thin section NPIII15‐2‐ 22 (Z33/1, N: 32 × 92); D, enlarged fragment shown by arrow in C. E, IGCAGS‐NP3‐617, thin section NPIII15‐2‐20 (V39, N: 38.3 × 96). F–G, IGCAGS‐CJ557, thin section CJ151.8‐16 (O33, N: 32.3 × 103); G, enlarged fragment shown by arrow in F.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

cavity. We consider this species synonymous with Appendisphaera tenuis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005, as mentioned above. The specimens attributed to the new combination Ericiasphaera fragilis (Moczydłowska, Vidal & Rudavskaya, 1993) comb. nov. by Grey (2005) have small conical portions of processes that are also hollow and freely communicate with the vesicle cavity, although their stem portions are narrow tubular, tapering and flexible. We retain the species Appendisphaera fragilis Moczydłowska, Vidal & Rudavskaya, 1993, emend. Moczydłowska, 2005. Ericiasphaera fibrilla n. sp. Figure 52 Holotype. – Specimen IGCAGS‐JQN192, thin section 11922‐2‐15, R37/2; illustrated in Figure 52A. Derivation of name. – From Latin fibra – thread, filament, fibre; referring to thin, filamentous processes. Locus typicus. – Yangtze Gorges area, Jiuqunao section. Stratum typicum. – Chert nodules in dolomite of the Doushantuo Formation, member II at a level of 31 m. Material. – 18 specimens at various state of preservation. Diagnosis. – Vesicle medium‐sized, spheroidal, bearing abundant, simple solid, thin filamentous, flexible processes that are very tightly located forming hairy corona around the vesicle outline. Processes are similar in length. Dimensions. – Vesicle diameter 73–125 μm (holotype 102 μm, x = 101.5 μm, δ = 13.6 μm); process length 16–38 μm (holotype 24 μm, x = 26 μm, δ = 5 μm) or 20–42.5% of vesicle diameter (holotype 23.5%, x = 25.9%, δ = 5.7%); n = 18. Remarks. – The very thin and fibrous processes do not show clearly their bases. The new species differs from E. magna by more abundant and densely arranged processes. Such density has not been observed in any other species of Ericiasphaera. Present record. – South China, Hubei Province, Yangtze Gorges area, Jiuqunao section, Doushantuo Formation, member II, Ediacaran.

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Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1988 Figure 53 1984 Comasphaeridium magnum sp. nov.; Zhang, Z., p. 98, pl. 1, figs 1–6. 1998 Ericiasphaera magna (Zhang Z. 1984) new combination; Zhang, Y., Yin L., Xiao & Knoll, 1998b, p. 28, figs 8:1, 2. 1998 Comasphaeridium magnum Zhang, 1984; Yuan & Hofmann, p. 197, fig. 6A, B. 1998 Ericiasphaera sp.; Yuan & Hofmann, p. 202, fig. 9A, B. 1998 Ericiasphaera sp.; Zhang, Yuan & Yin, 1998a, p. 1783a, fig. 1c. 1998 Ericiasphaera magna (Zhang); Zhang, Y., Yuan, X. and Yin L., 1998a, p. 1783a, fig. 3. 2002 Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1998; Yuan, X., Xiao, S., Yin, L., Knoll, A.H., Zhou, C. & Mu, X., p. 74, figs 95, 96. 2007 Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1998; Yin, C., Liu, Y., Gao, L., Wang, Z., Tang, F. & Liu, P., pl. 17, figs 1, 2. 2007 Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1998; Yin L., Zhu, M., Knoll, A.H., Yuan, X., Zhang, J. & Hu, J., p. 661, fig. 1a. 2007 Eotintinopsis pinniforma gen. et sp. nov.; Li, C., Chen, J., Lipps, J., Gao, F., Chi, H. & Wu, H., p. 153, fig. 1a, b. 2010 Eotintinopsis pinniforma (Dunthorn et al. 2010); Dunthorn, Lipps & Stoeck, p. 141, fig. 1a, b. 2014 Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1998; Xiao, S., Zhou, C., Liu, P., Wang, D. & Yuan, X. 2014a, pp. 20, 22, fig. 13:1–5. 2014 Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1998; Liu, P. Xiao, S., Yin, C., Chen, S., Zhou, C. & Li, M., 2014b, p. 75, fig. 34:1–10 2017 Ericiasphaera sp.; Hawkins, Xiao, Jiang, Wang & Shi, fig. 8A, B.

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Fig. 52. A–F, Ericiasphaera fibrilla n. sp. A, holotype, IGCAGS‐JQN192, thin section 11922‐2‐15 (R37/2, N: 36.5 × 100). B, IGCAGS‐ JQN033, thin section JQN‐1‐14 (P47/1, N: 45.5 × 102.4). C, IGCAGS‐JQN044, thin section JQN‐1‐18 (K29/4, N: 28.7 × 106.4). D, IGCAGS‐JQN024, thin section JQN‐1‐11 (Q42, N: 41.4 × 101). E, IGCAGS‐JQN184, thin section 11922‐2‐10 (R38, N: 37.1 × 100). F, IGCAGS‐JQN188, thin section 11922‐2‐11 (U31/4, N: 36 × 106.2). All specimens demonstrate diagnostic densely arranged, solid filamentous processes.

FOSSILS AND STRATA

Ediacaran microfossils from the Doushantuo Formation

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Fig. 53. A–D, Ericiasphaera magna (Zhang, 1984) Zhang, Yin L., Xiao & Knoll, 1988. A, IGCAGS‐WF‐80, thin section WFG22.4‐10 (P41/ 2, Z: 107 × 10). B, IGCAGS‐WFG‐20, thin section WFG9.4‐8 (J45, Z: 104 × 17.8). C, IGCAGS‐NP1‐21, thin section NP6‐4‐1 (L41/1, N: 40.3 × 96.7). D, IGCAGS‐SXF38, thin section SXF1.4‐33 (L45, Z: 100 × 17).

Material. – 10 well‐preserved specimens. Description. – Vesicle large, spheroidal, bearing abundant but separated from one another solid processes, uniform in shape, cylindrical and thin, with sharp‐pointed or blunt tips. Dimensions. – Vesicle diameter 139–533 μm (x = 276 μm, n = 10); process length 14–51 μm (x = 32 μm, n = 10) or 8.5–18% of the vesicle diameter (x = 12.1%, n = 10); process width