Papers from the 6th International Conference on Trilobites and their Relatives 9781119564249, 1119564247

Table of contents :
Cover......Page 1
Acknowledgements......Page 3
Contents......Page 4
Papers from the 6th International Conference on Trilobites and their Relatives......Page 7
References......Page 8
Oslo, Norway 1973 (July 1–8)......Page 11
Brock University, St. Catharines, Ontario, Canada 1997 (August 22–25)......Page 14
University of Oxford, England, 2001 (April 3–6)......Page 17
Toledo, Spain, 2008 (June 16–24)......Page 20
Prague, Czech Republic, 2012 (July 1–4)......Page 21
References......Page 22
The 6th International Conference on Trilobites and their Relatives: Tallinn calling, Estonia celebrating......Page 23
Acknowledgements......Page 26
References......Page 27
Introduction......Page 29
Geological setting......Page 30
Trilobite early stages......Page 31
Possible trilobite eggs......Page 33
Concluding remarks......Page 36
References......Page 37
Introduction......Page 41
Structural setting......Page 42
Units, ages and fossils......Page 44
Engelgardt Formation (Èngel’gardtovskaâ Svita)......Page 46
Barkov Formation (Barkovskaâ Svita)......Page 47
Povorotnaya Formation (Povorotninskaâ svita)......Page 48
Biofacies......Page 49
Scoto-Appalachian comparison......Page 54
Acknowledgements......Page 55
References......Page 56
Introduction......Page 61
Tiout section......Page 62
Tazemmourt section......Page 64
Trilobite occurrence, diversity and biostratigraphy......Page 66
Biostratigraphical implications and biochronological framework......Page 68
Systematic palaeontology......Page 69
References......Page 156
Introduction......Page 161
Stratigraphical context......Page 162
Systematic Palaeontology......Page 163
Notes on palaeoecology and palaeoenvironments......Page 172
Acknowledgements......Page 174
References......Page 175
Introduction......Page 179
Geological setting......Page 180
Results and discussion......Page 182
Systematic palaeontology......Page 184
References......Page 195
Introduction......Page 199
Trilobite fauna......Page 200
Taphonomy......Page 201
References......Page 208
Introduction......Page 211
Geological background......Page 212
Material and methods......Page 213
Palaeoecology......Page 214
Connections with Chinese and peri-Gondwanan terranes......Page 217
Systematic palaeontology......Page 218
References......Page 236

Citation preview

Papers from the 6th International Conference on Trilobites and their Relatives Edited by

Alan W. Owen and David L. Bruton

Dedication This volume is dedicated to the memories of Leif Størmer, Gunnar Henningsmoen and Valdar Jaanusson who were instrumental in the organisation of the first trilobite meeting held in Oslo in 1973. Each also made considerable contributions to the first trilobite treatise published in 1959. It is also fitting for a volume arising from the meeting in Tallinn that Valdar Jaanusson was born in Estonia and studied in Tallinn before fleeing to Sweden in 1944. Acknowledgements Financial support for the publication of this issue of Fossils and Strata was provided by the Lethaia Foundation

Contents Papers from the 6th International Conference on Trilobites and their Relatives By Alan W. Owen & David L. Bruton . . . . 1 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 From Oslo to Prague – the Trilobite meetings 1973–2012 By David L. Bruton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Oslo, Norway 1973 (July 1–8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Brock University, St. Catharines, Ontario, Canada 1997 (August 22–25) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 University of Oxford, England, 2001 (April 3–6) . . . . . . . . . . . . . 11 Toledo, Spain, 2008 (June 16–24) . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Prague, Czech Republic, 2012 (July 1–4) . . . . . . . . . . . . . . . . . . . . 15 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 The 6th International Conference on Trilobites and their Relatives: Tallinn calling, Estonia celebrating By Helje Pärnaste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Early post‐embryonic trilobite stages and possible eggs from the ‘Túnel Ordovícico del Fabar’ (Middle Ordovician, northwestern Spain) By Enrique Bernárdez, Jorge Esteve, Lukáš Laibl, Isabel Rábano and Juan Carlos Gutiérrez-Marco . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Geological setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Trilobite early stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Possible trilobite eggs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Stratigraphy and trilobite biofacies of the Late Ordovician of the Taimyr Peninsula, Arctic Russia By Jan Ove R. Ebbestad & Richard A. Fortey . . . . . . . . . . . . . . 35 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 The Taimyr Peninsula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Geography and previous research . . . . . . . . . . . . . . . . . . . . . . . 36 Structural setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Facies regions and areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Stratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Units, ages and fossils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Vesenn’aya Formation (Vesenninskaâ tolŝa) . . . . . . . . . . . . . . . 40 Toll Formation (Tollevskaâ Svita) . . . . . . . . . . . . . . . . . . . . . . . . 40 Engelgardt Formation (Èngel’gardtovskaâ Svita) . . . . . . . . . . . 40 Tolmachev Formation (Tolmačevskaâ Svita) . . . . . . . . . . . . . . 41 Barkov Formation (Barkovskaâ Svita) . . . . . . . . . . . . . . . . . . . . 41 Mutnyj Formation (Mutninskaâ svita) . . . . . . . . . . . . . . . . . . . 42 Povorotnaya Formation (Povorotninskaâ svita). . . . . . . . . . . . 42 Trilobite distribution and biofacies . . . . . . . . . . . . . . . . . . . . . . . . . 43 Stratigraphical distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Biofacies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Scoto‐Appalachian comparison . . . . . . . . . . . . . . . . . . . . . . . . . 48 Barkov Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 The earliest known West Gondwanan trilobites from the Anti‐Atlas of Morocco, with a revision of the Family Bigotinidae Hupé, 1953 By Gerd Geyer. . . . . . . . . . . . . . . . . . . 55 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Geological setting and stratigraphy of the Anti‐Atlas sections . . . 56 Tiout section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Igoudine Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Amouslek Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Tazemmourt section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Amouslek section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Trilobite occurrence, diversity and biostratigraphy . . . . . . . . . . . 60 Trilobite preservation and preparation . . . . . . . . . . . . . . . . . . . . . 62 Biostratigraphical implications and biochronological framework. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Systematic palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Class Trilobita Walch, 1771 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Order Redlichiida Richter, 1932 . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Suborder Redlichiina Richter, 1932 . . . . . . . . . . . . . . . . . . . . . . . . 64 Family Bigotinidae Hupé, 1953 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Genus Bigotina Cobbold, 1935 . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Bigotina bivallata Cobbold, 1935 . . . . . . . . . . . . . . . . . . . . . . 73 Bigotina kelleri n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 Bigotina monningeri n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Bigotina sp. A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Bigotina sp. B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Bigotina angulata Suvorova, 1960 . . . . . . . . . . . . . . . . . . . . . 87 Bigotina inornata Egorova, 1986 . . . . . . . . . . . . . . . . . . . . . . 89 Genus Bigotinella Suvorova, 1960 . . . . . . . . . . . . . . . . . . . . . . . 90 Bigotinella malykanica (Suvorova, 1960 ) . . . . . . . . . . . . . . 92 Genus Bigotinops Hupé, 1953 . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Bigotinops dangeardi Hupé, 1953 . . . . . . . . . . . . . . . . . . . . . . 94 Bigotinops chouberti n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Genus Ouijjania Hupé, 1953 . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Ouijjania meridionalis Hupé, 1953 . . . . . . . . . . . . . . . . . . . 102 Genus Demuma Özdikmen, 2009 . . . . . . . . . . . . . . . . . . . . . . 104 Demuma nicklesi (Hupé, 1953) . . . . . . . . . . . . . . . . . . . . . . 104 ‘Demuma bourgini (Hupé, 1953)’ . . . . . . . . . . . . . . . . . . . . 106 Genus Issendalenia n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Issendalenia grandispina n. gen., n. sp. . . . . . . . . . . . . . . . 106 Genus Tioutella n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Tioutella floccofavosa n. gen., n. sp. . . . . . . . . . . . . . . . . . . 109 Genus Pseudobigotina n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Pseudobigotina antiatlasensis n. gen., n. sp. . . . . . . . . . . . . 113 Genus Hupetina Sdzuy, 1978. . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Hupetina antiqua Sdzuy, 1978 . . . . . . . . . . . . . . . . . . . . . . . 116 Genus Serrania Liñán, 1978 . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Serrania verae Liñán, 1978 . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Genus Eladiolinania n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Eladiolinania castor n. gen., n. sp. . . . . . . . . . . . . . . . . . . . 122 Eladiolinania pollux n. gen., n. sp. . . . . . . . . . . . . . . . . . . . 125 Eladiolinania? palaciosi (Liñán, Gozalo, Dies Álvarez, Gámez Vintaned & Zamora, 2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Eladiolinania? gordaensis (Liñán, Gozalo, Dies Álvarez, Gámez Vintaned & Zamora, 2008) . . . . . . . . . . . . . . . . 127 Genus Suvorovaella n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Suvorovaella priva (Suvorova, 1960) . . . . . . . . . . . . . . . . . . 129 Suvorovaella? patria (Suvorova, 1960) . . . . . . . . . . . . . . . . 131 Genus and species indeterminate A . . . . . . . . . . . . . . . . . . . . . 131 Genus and species indeterminate B . . . . . . . . . . . . . . . . . . . . . 132 Genus and species indeterminate C . . . . . . . . . . . . . . . . . . . . . 133 Genus and species indeterminate D . . . . . . . . . . . . . . . . . . . . . 133 Genus and species indeterminate E . . . . . . . . . . . . . . . . . . . . . 133 Family Minusinellidae n. fam. . . . . . . . . . . . . . . . . . . . . . . . . . . `134 Minusinella Repina, 1960 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Family indeterminate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Genus and species indeterminate F . . . . . . . . . . . . . . . . . . . . . 135 Superfamily Fallotaspidoidea Hupé, 1953 . . . . . . . . . . . . . . . . . . 135 Family Fallotaspididae Hupé 1953 . . . . . . . . . . . . . . . . . . . . . . . . 135 Genus Eofallotaspis Sdzuy, 1978 . . . . . . . . . . . . . . . . . . . . . . . . 135 Eofallotaspis tioutensis Sdzuy, 1978 . . . . . . . . . . . . . . . . . . . 137 Eofallotaspis prima Sdzuy, 1978 . . . . . . . . . . . . . . . . . . . . . . 141 Genus Debrenella n. gen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 Debrenella larvalis n. gen., n. sp. . . . . . . . . . . . . . . . . . . . . . 145 Genus Fallotaspis Hupé, 1953 . . . . . . . . . . . . . . . . . . . . . . . . . . 146 Fallotaspis plana Hupé, 1953, emend. . . . . . . . . . . . . . . . . . 146 Fallotaspis antecedens n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . 149 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

The nileid trilobite Symphysurus from upper Tremadocian strata of the Moroccan Anti‐Atlas: taxonomic reappraisal and palaeoenvironmental implications By Juan Carlos Gutiérrez-Marco, Isabel Rábano & Diego C. García-Bellido . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Stratigraphical context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Systematic Palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Order Asaphida Salter, 1864 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Superfamily ?Cyclopygoidea Raymond, 1925 . . . . . . . . . . . . . . . 157 Family Nileidae Angelin, 1854. . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Genus Symphysurus Goldfuss, 1843. . . . . . . . . . . . . . . . . . . . . 157 Symphysurus ebbestadi n. sp. . . . . . . . . . . . . . . . . . . . . . . . . 158 Symphysurus sicardi (Bergeron, 1895) . . . . . . . . . . . . . . . . 164 Symphysurus? n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 Notes on palaeoecology and palaeoenvironments . . . . . . . . . . . 166 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Trilobite‐based biostratigraphy of the Xiaoshiba Lagerstätte By Jin-Bo Hou, Jie Yang, Xi-Guang Zhang, Nigel C. Hughes & Tian Lan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Geological setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Systematic palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Class Trilobita Walch, 1771 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Order Redlichiida Richter, 1933 . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Suborder Redlichiina Harrington, 1959 (in Harrington et al., 1959) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Superfamily Ellipsocephalacea Matthew, 1887 . . . . . . . . . . . . . . 178 Family Yunnanocephalidae Hupé, 1953 . . . . . . . . . . . . . . . . . . . 178 Genus Yunnanocephalus Kobayashi, 1936 . . . . . . . . . . . . . . . 178 Yunnanocephalus yunnanensis (Mansuy, 1912) . . . . . . . . 178 Superfamily Redlichiacea Poulsen, 1927 . . . . . . . . . . . . . . . . . . . 180 Family Dolerolenidae Kobayashi, 1951 (in Kobayashi & Kato, 1951) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 Genus Dolerolenus Leanza, 1949 . . . . . . . . . . . . . . . . . . . . . . . 181 Subgenus Dolerolenus (Malungia) Lu, 1961 . . . . . . . . . . . . 181 Dolerolenus (Malungia) laevigata Lu, 1961. . . . . . . . . . . . . . . 181 Family Gigantopygidae Harrington, 1959 (in Harrington et al., 1959) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 Subfamily Yiliangllinae Zhang & Lin, 1980 (in Zhang et al., 1980). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 Genus Zhangshania Li & Zhang, 1990 (in Li et al., 1990) . . . . 182 Zhangshania typica Li & Zhang, 1990 . . . . . . . . . . . . . . . . . 182 Variant of Z. typica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Family Metadoxididae Whitehouse, 1939 . . . . . . . . . . . . . . . . . . 185 Genus Hongshiyanaspis Zhang & Lin, 1980 . . . . . . . . . . . . . . 185 Hongshiyanaspis yiliangensis Zhang & Lin, 1980 . . . . . . . 185 Family Redlichiidae Poulsen, 1927 . . . . . . . . . . . . . . . . . . . . . . . . 185 Subfamily Wutingaspinae Chang, 1966 . . . . . . . . . . . . . . . . . . . . 185 Genus Chengjiangaspis Zhang & Lin, 1980 . . . . . . . . . . . . . . 185 Chengjiangaspis chengjiangensis Zhang & Lin, 1980 . . . . 186 Genus Kuanyangia Hupé, 1953 . . . . . . . . . . . . . . . . . . . . . . . . 187 Kuanyangia pustulosa Lu, 1941 . . . . . . . . . . . . . . . . . . . . . . 187 Kuanyangia shaanxiensis Zhang & Lin, 1980 . . . . . . . . . . 188 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

The taphonomy of a trilobite fauna from an uppermost Katian echinoderm Lagerstätte in South West Wales By Lucy M. E. McCobb, Patrick D. McDermott & Alan W. Owen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 The Llanddowror bypass echinoderm Lagerstätten . . . . . . . . . . 194 Trilobite fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Taphonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 The Silurian and Devonian proetid and aulacopleurid trilobites of Japan and their palaeogeographical significance By Christopher P. Stocker, Derek J. Siveter, Philip D. Lane, Mark Williams, Tatsua Ojl, Gengo Tanaka, Toshifumi Komatsu, Simon Wallis, David J. Siveter & Thijs R. A. Vandenbroucke . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Geological background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 Palaeoecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 Palaeobiogeography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Intra-Japanese terrane palaeobiogeography . . . . . . . . . . . . . . 211 Connections with Chinese and peri-Gondwanan terranes . . . 211 Systematic palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 Order Proetida Fortey & Owens, 1975. . . . . . . . . . . . . . . . . . . . . 212 Family Proetidae Salter, 1864 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 Subfamily Proetinae Salter, 1864 . . . . . . . . . . . . . . . . . . . . . . . . . . 212 Genus Coniproetus Alberti, 1966 . . . . . . . . . . . . . . . . . . . . . . . 212 Coniproetus subovalis (Kobayashi & Hamada,1974) . . . . 212 Coniproetus sp. A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 Genus Ganinella Yolkin, 1968 . . . . . . . . . . . . . . . . . . . . . . . . . . 214 Ganinella tenuiceps (Kobayashi & Hamada, 1987) . . . . . . 215 Ganinella fukujiensis (Kobayashi & Hamada,1977) . . . . . 216 Ganinella oisensis (Kobayashi & Hamada, 1977) . . . . . . . 218 Genus Gomiites Pr˘ibyl & Vanĕk, 1978 . . . . . . . . . . . . . . . . . . . 219 Gomiites granulatus (Kobayashi & Hamada, 1974) . . . . . 220 Gomiites latiaxis (Kobayashi & Hamada, 1986) . . . . . . . . 222 Subfamily Crassiproetinae Osmólska, 1970 . . . . . . . . . . . . . . . . 223 Genus Hedstroemia Pr˘ibyl & Vanĕk, 1978 . . . . . . . . . . . . . . . 223 Hedstroemia sugiharensis (Kobayashi & Hamada,1974) . . . 223 Subfamily Cornuproetinae Richter et al. in Moore, 1959 . . . . . 224 Genus Interproetus Šnajdr, 1977 . . . . . . . . . . . . . . . . . . . . . . . . 224 Interproetus mizobuchii n. sp. . . . . . . . . . . . . . . . . . . . . . . . 224 Subfamily Eremiproetinae Alberti, 1967 . . . . . . . . . . . . . . . . . . . 226 Genus Eremiproetus Richter & Richter, 1919 . . . . . . . . . . . . . 226 Eremiproetus? subcarinatus (Kobayashi & Hamada, 1974) . . 226 Eremiproetus? magnicerviculus (Kobayashi & Hamada, 1974) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Subfamily Dechenellinae Pr˘ibyl, 1946 . . . . . . . . . . . . . . . . . . . . . 227 Genus Dechenella Kayser, 1880 . . . . . . . . . . . . . . . . . . . . . . . . . 227 Dechenella minima Okubo, 1951 . . . . . . . . . . . . . . . . . . . . . 227 Subfamily Warburgellinae Owens, 1973 . . . . . . . . . . . . . . . . . . . 228 Genus Latiproetus Lu, 1962 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Latiproetus bilobus (Kobayashi & Hamada, 1974) . . . . . . 228 Order Aulacopleurida Adrain, 2011 . . . . . . . . . . . . . . . . . . . . . . . 229 Family Aulacopleuridae Angelin, 1854 . . . . . . . . . . . . . . . . . . . . 229 Subfamily Otarioninae Richter & Richter, 1926 . . . . . . . . . . . . . 229 Genus Maurotarion Alberti, 1969 . . . . . . . . . . . . . . . . . . . . . . 229 Maurotarion megalops (Kobayashi & Hamada, 1977) . . . 229 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Papers from the 6th International Conference on Trilobites and their Relatives ALAN W. OWEN AND DAVID L. BRUTON

Owen, A.W., Bruton, D.L. 2019: Papers from the 6th International Conference on Trilobites and their Relatives. Fossils and Strata, No. 64. pp. 1–3. This volume arises from the 6th International Conference on Trilobites and their Relatives held in Tallinn, Estonia, in July 2017. Seven papers on trilobites are included in the volume and are briefly summarized here. They range from systematic descriptions of taxa to considerations of ontogeny, biofacies, biostratigraphy and taphonomy, and together, they encompass trilobites from the Early Cambrian to the Late Devonian. The volume also includes a report of the Tallinn conference and a review of those that went before it. □ Cambrian, Devonian, Ordovician, Silurian, Tallinn conference, trilobites. Alan W. Owen [[email protected]], School of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens Glasgow G12 8QQ, UK; David L. Bruton [[email protected]], Natural History Museum (Palaeontology), University of Oslo, Postboks 1172 Blindern, NO-0318 Oslo, Norway; manuscript received on 1/06/2018; manuscript accepted on 6/07/2018.

The proceedings of the first International Conference on Trilobites and their Relatives held in Oslo in 1973 (Bruton 2019) were published in one of the earliest editions of Fossils and Strata (Martinsson 1975). It is highly fitting, therefore, that with the return of the conference to Baltoscandia (P€arnaste 2018), the Lethaia Foundation, under whose auspices Fossils and Strata is published, kindly offered to publish a volume of papers arising from the sixth meeting held in Tallinn, Estonia, in July 2017. The papers in the volume vary considerably in length. Although a notional page limit was given, it was made clear from the outset that there was some flexibility in this. The submission of a manuscript of almost monographic proportions (Geyer 2019) stretched this flexibility beyond what we had originally envisaged but the evident importance of the submission convinced us that it should be included. Geyer describes the remarkably diverse trilobite fauna from the lower Cambrian in the Anti-Atlas of Morocco, particularly the important global reference Tiot section. This fauna is crucial to the understanding of the earliest history of the trilobites and to the concept and correlation of Cambrian Series 2 and Stage 3. In the latter context, it enables a revised subdivision of the lowest of the Moroccan trilobite biozones. The paper includes descriptions of some 35 species, of which ten are new as are six genera. It includes description of the oldest unequivocally determinable trilobites from western Gondwana and possibly the world. The overall reassessment of the Bigotinidae

involves revision of genera and species from other countries and the establishment of a new family within the Redlichiida. Trilobites from the lower Cambrian are also described by Hou et al. (2019) from the Xiaoshiba Lagerst€atte in Kunming, southern China. Whilst none of the described taxa are new, their description based on well-preserved material and their precisely located occurrences in measured sections points to the utility of some taxa in the eventual establishment of a robust species-based biostratigraphical division of the lower Cambrian of southern China. In particular, such a scheme of trilobite biozones should enhance the correlation of the successive Chengjiang, Xiaoshiba and Malong soft-bodied assemblages. Trilobites from another exceptionally preserved fauna, the upper Tremadocian Fezouata Lagerst€atte of the Moroccan Anti-Atlas, are described by Gutierrez-Marco et al. (2019). These occur in large numbers in monospecific assemblages and belong to a new species of the nileid Symphysurus. A second species, Symphysurus sicardi (Bergeron), is described from a slightly higher horizon, close to the Tremadocian–Floian boundary and a third, possibly new, but not named, species is described from the upper Tremadocian. Gutierrez-Marco et al. discuss the likely environmental setting indicated by the new Moroccan records of Symphysurus which in turn leads to the understanding of what has become a highly significant Lagerst€atte. Trilobites in yet another Lagerst€atte are the subject of a taphonomic study by McCobb et al. (2019). Recent collecting in the largely neglected, upper

DOI 10.1002/9781119564232 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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A. W. Owen & D. L. Bruton

Katian, Slade and Redhill Mudstone Formation in South West Wales has revealed a large number of fossiliferous localities including one in which there are three thin echinoderm Lagerst€atten. One of these also contains a rich trilobite fauna in addition to a diverse range of articulated echinoderms. Unlike the other faunas recovered from the formation, illaenids (including several enrolled specimens) dominate the trilobite fauna and complete exoskeletons are more common. Whilst disarticulated remains represent already dead or moulted individuals, the other aspects of the trilobite fauna provide the same taphonomic signal as the echinoderms – the rapid transport and burial of living animals, leading to their death. Lagerst€atten have provided increasingly important insights into trilobite morphology and taphonomy over recent years. Considerable advances have also been made in understanding trilobite ontogeny, again an area of investigation dependent on aspects of unusual preservation. Bernardez et al. (2019) document early growth stages of the calymenacean trilobite Prionocheilus mendax (Vanek) preserved in fine-grained mudstones in the Darriwilian (Middle Ordovician) Cofi~ no Member of the Sueve Formation in northwestern Spain. These range from protaspides to meraspid degree 2 and include in situ exuviae with disarticulated librigenae. Clusters of pyrite spheres from the Bayo Member of the same formation are interpreted as possibly being trilobite eggs and are associated with the pliomerid Placoparia (Coplacoparia) tournemini. (Rouault). Both the calymenid larvae and the possible eggs are relatively large in relation to comparative material from elsewhere, and Bernardez et al. raise the possibility that this may reflect lecithotrophy related to higher latitudes and/ or the scarcity of organic matter. Two papers in this volume address faunas that are in major need of revision, in terms of both material described decades ago and new collections: Ebbestad & Fortey (2019) discuss the Upper Ordovician faunas of the Taimyr Peninsula in terms of their distribution within the modern lithostratigraphical and lithofacies framework and assess the biofacies into which these faunas fall. They use R- and Q-mode cluster analysis to identify two distinct biofacies. Black limestone and shales are typified by what they term the ‘raphiophorid association’ with many taxa very like those of the peripheral Laurentian Scoto-Appalachian faunas. In contrast, shelf limestones contain the ‘the monorakine–cheirurid–illaenid association’ which comprises a diverse range of monorakine genera endemic to the Siberian palaeoplate together with Calyptaulax, isotelines and cheirurids that also typify inshore settings on Laurentia.

FOSSILS AND STRATA

Stocker et al. (2019) provide a very thorough taxonomic revision of all previously described trilobites belonging to the orders Proetida and Aulacopleurida from the Silurian and Devonian of Japan, along with descriptions of new material. Together this comprises 13 named species, one of which is new, belonging to nine genera, with three species described under open nomenclature. Stocker et al. identify species-level endemicity amongst these trilobites both compared to other East Asian terranes and between individual Japanese terranes. They argue that this endemicity may reflect palaeoenvironmental differences rather than simply geographical isolation.

Acknowledgements We are extremely grateful to the Lethaia Foundation and, in particular the chairman, Hans Arne Nakrem, for publishing this volume. We are also grateful to Svend Stouge, Editor-in-Chief of Fossils and Strata for his hard efforts in seeing this volume through to production. Sincere thanks must also go to the reviewers of the papers: Per Ahlberg, Brian Chatterton, Euan Clarkson, Andrei Dronov, Thomas Hegna, David Holloway, Michal Mergl, Frank Nikolaisen, Bob Owens, Alan Thomas, Xue-Jian Zhu, Anna _ nska and three anonymous referees. Zyli

References Bernardez, E., Esteve, J., Laibl, L., Rabano, I. & Gutierrez-Marco, J.C. 2019: Early post-embryonic trilobite stages and possible eggs from the ‘T unel Ordovıcico del Fabar’ (Middle Ordovician, northwestern Spain). Fossils and Strata 64, 23–33, (this volume). Bruton, D.L. 2019: From Oslo to Prague – the Trilobite Meetings 1973–2012. Fossils and Strata 64, 5–16, (this volume). Ebbestad, J.O.R. & Fortey, R.A. 2019: Stratigraphy and trilobite biofacies of the Late Ordovician of the Taimyr Peninsula, Arctic Russia. Fossils and Strata 64, 35–53, (this volume). Geyer, G. 2019: The earliest known West Gondwanan trilobites from the Anti-Atlas of Morocco, with a revision of the Family Bigotinidae Hupe, 1953. Fossils and Strata 64, 55–153, (this volume). Gutierrez-Marco, J.C., Rabano, I. & Garcıa-Bellido, D.C. 2019: The nileid trilobite Symphysurus from upper Tremadocian strata of the Moroccan Anti-Atlas: taxonomic reappraisal and palaeoenvironmental implications. Fossils and Strata 64, 155– 171 (this volume). Hou, J.B., Yang, J., Zhang, X.G., Hughes, N. & Lan, T. 2019: Trilobite-based biostratigraphy of the Xiaoshiba Lagerst€atte. Fossils and Strata 64, 173–191, (this volume). Martinsson, A. (ed.) 1975: Evolution and morphology of the Trilobita, Trilobitoidea and Merostomata. Fossils and Strata 4, 1–467. McCobb, L.M.E., McDermott, P.D. & Owen, A.W. 2019: The taphonomy of a trilobite fauna from an uppermost Katian echinoderm Lagerst€atte in South West Wales. Fossils and Strata 64, 193–203, (this volume).

FOSSILS AND STRATA P€arnaste, H. 2019: The 6th International Conference on Trilobites and their Relatives: Tallinn calling, Estonia celebrating. Fossils and Strata 64, 17–22 (this volume). Stocker, C.P., Siveter, D.J., Lane, P.D., Williams, M., Oji, T., Tanaka, G., Komatsu, T., Wallis, S., Siveter, D.J. &

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Vandenbroucke, T.R.A. 2019: The Silurian and Devonian proetid and aulacopleurid trilobites of Japan and their palaeogeographical significance. Fossils and Strata 64, 205–232, (this volume).

From Oslo to Prague – the Trilobite meetings 1973–2012 DAVID L. BRUTON Bruton, D. L. 2019: From Oslo to Prague – the Trilobite meetings 1973–2012. Fossils and Strata, No. 64, pp. 5–16. The following report is a personal account of the first five trilobite symposia from Oslo 1973 to Prague 2012 and some of the people who made these meetings so rewarding. In addition to providing a focus for a very active research community, all the symposia with associated field trips have given me the chance to become better acquainted with new faces and to forge lasting friendships. □ International trilobite conferences, Oslo, Oxford, Prague, St Catharines, Toledo. David L. Bruton [[email protected]], Natural History Museum (Palaeontology), University of Oslo, Postboks 1172 Blindern NO-0318 Oslo, Norway; manuscript received on 1/06/2018; manuscript accepted on 6/07/2018.

Introduction As the instigator and organizer of the first conference, held in Norway in 1973, I am delighted that others in our very active research community have followed my lead and convened further meetings on trilobites and other early arthropods. All the symposia with associated field trips have given me the chance to become better acquainted with new faces and to forge friendships which have lasted to the present. In this respect, I thank Fred Shaw, Richard Fortey, Derek Siveter and Derek Briggs all of whom were in Oslo in 1973 and have attended all of the meetings with me since then.

A summary of what is written here formed the basis for my talk at the most recent meeting, held in Tallinn in July 2017. It provides a personal account of the five meetings that preceded it.

Oslo, Norway 1973 (July 1–8) During my Ph.D studies (1962–1965), I had the great privilege of meeting with some of the big names working with trilobites both in Europe and North America. Three in Scandinavia come to mind, Valdar Jaanusson in Stockholm and, in Oslo, Gunnar Henningsmoen and Leif Størmer (Fig. 1). It was Størmer who encouraged me to return to Oslo when I was

Fig. 1. Oslo 1973: The scientific committee. A, Leif Størmer; B, Gunnar Henningsmoen; C. Valdar Jannuson. Photographs: Natural History Museum, Oslo. DOI 10.1002/9781119564232 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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Fig. 2. Oslo 1973: Group gathering on the lawn of Voksen
asen conference centre just before the meeting banquet on July 7. Key to photograph: 1. Gunnar Henningsmoen. 2. Kari Henningsmoen. 3. Mike Romano. 4. John Cisne. 5. Jim Stitt. 6. Mrs. Stitt. 7. Anne Bruton. 8. David Bruton. 9. Chris Hughes. 10. Dian Teigler. 11. Harry Whittington. 12. Bob Hessler. 13. Derek Siveter. 14. Pierre Lesperance. 15. Natascha Heintz. (organization). 16. Leif Størmer. 17. Valdar Jaanusson. 18. Alberto Simonetta. 19. Ken McNamara. 20. Ken Towe. 21. Mrs Waterston. 22. Charles Waterston. 23. Derek Briggs. 24. Brian Norford. 25. Peter Jell. 26. Ken Campbell. 27. T. Hamada. 28. Dan Fisher. 29. Helmut Alberti. 30. Halszka Osmolska. 31. Mrs Hamada. 32. Allen Ormiston. 33. Fred Shaw. 34. Niles Eldredge. 35. Mrs. Eldredge. 36. Phil Lane. 37. Keith Ingham. 38. Tutti Størmer. 39. Sir James Stubblefield. 40. Ewa Tomczykowa. 41. Lady Stubblefield. 42. Jill Ross. 43. Mrs. Hessler. 44. Rube Ross. 45. Dorothy Whittington. 46. Maureen Hughes. 47. Pierre Morzadec. 48. Richard Fortey. 49. Jacques Destombes. 50. Mrs. Henry. 51. Jean-Louis Henry. 52. Alan Thomas. 53. John Temple. 54. Dick Robison. 55. Judy Shergold. 56. Bob Owens. 57. John Shergold. 58. Mrs. Dean. 59. Bill Dean. 60. Tove Bockelie (organization). 61. Jan Bergstr€ om. 62. John Dalingwater. 63. Euan Clarkson. Not present when the photograph was taken: Ladislav Marek and Mrs Marek, P. Chardy, David Schwimmer and Riccardo Levi-Setti. Photograph: Johan Fredrik Bockelie.

finished with my thesis and later was behind my employment at the University in 1967. Within a year, the first trilobite meeting was being planned with Leif, Gunnar and Valdar supporting me as organizer. Tutti Størmer and my wife, Anne, took care of the accounts; no mean task as the strength of the dollar changed at the time. This was before pocket calculators were in widespread use and Anne used her slide rule with great success. The Norwegian scientist Gunnar Randers was, at this time, head of the NATO Scientific Affairs Division, and when approached, he

suggested we should apply for funding as Norway had not done this to any great extent and there was plenty of money available. We applied and were awarded USD 10,000. From IUGS, we received USD 1,000 while smaller sums came from the Norwegian Research Council and the IPA. With this, we were able to invite 60 participants from 13 nations (Fig. 2) and pay all travel and accommodation for the three-day meeting with the addition of an excursion to classic localities in the Oslo Region. The meeting made a profit which

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covered the publication costs of the proceedings (Martinsson 1975). I worked with Harry Whittington at Harvard in 1964, and we were together for the second Burgess Shale expedition in 1967 (Bruton 2011). Leif Størmer, who had worked on the Burgess fauna, thought this was a good chance to include this on the programme and thus Harry lectured on the limbs of Olenoides. Also in the programme, John Cisne described the limbs of Triarthrus. This, I think, was the start of a focus on arthropod appendages, their form, function and use in high-level taxonomy which blossomed as further results from the Burgess Shale arthropod fauna became known and the term ‘Trilobitomorpha’ received a new meaning. Richard Fortey’s contribution on trilobite communities later became a classic in the study of community palaeoecology. The organizers were especially interested in inviting non-trilobite workers and, to this end, contributions on Limulus by Daniel C. Fisher, on eurypterids by Charles D. Waterston and the relations of the trilobitomorpha to the crustaceans by Robert R. Hessler, provided for much discussion. All these are to be found in the extensive volume arising from the meeting (Martinsson 1975). The meeting sessions and accommodation were in an attractive conference centre high up in the

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Fig. 3. Oslo 1973: Conference excursion. Quarry with shales and Ogygiocaris. From the left: Euan Clarkson, David Bruton and Leif Størmer. Photograph: Brian Norford.

forest and overlooking the city of Oslo. The weather was perfect for an excursion by boat on the Oslo fjord and localities visited both ashore and on islands (Fig. 3). The excursion day ended with an unexpected thunder storm in the late afternoon forcing participants to run through town to board a private tram that took them nonstop to the conference centre. The group photograph (Fig. 2) was taken before the conference dinner and after all had dried out. The year 1973 precluded participation from China and the fact that the meeting was

Fig. 4. St. Catharines, 1997: Outside conference centre, Brock University, Ontario, Canada. From the left: Joanne Klussendorf, Don Mikulic, Derek Siveter (partly hidden), Nigel Hughes, Suraj K. Parcha, Dave Rudkin, Tatyana Pegel, Rudolfo Gozalo. Photograph: Dave Rudkin.

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Fig. 5. St. Catharines, 1997: Group picture. Key to photograph. Back row: 1. Hans-Hartmut Krueger. 2. Margaret Campbell. 3. Ingrid Krueger. 4? 5. Derek Siveter. 6. Robert Sensenstein. 7. Miriam Zelditch. 8. Helje P€arnaste. 9. Danita Brandt. 10. Joanne Kluessendorf. 11. ? Mark Webster. 12. Ralph Chapman. 13. Nigel Hughes. 14. Rolf Ludvigsen. 15. Brian Chatterton. 16. Tim McCormick. 17. Denis Tetreault. 18. Richard Fortey. 19. ?John Taylor. 20. Michael Cuggy. 21. David Rudkin. 22. Stephen Westrop. 23. ?Chris Nedin. 24.? 25. Tatyana Pegel. 26. Donald Mikulic. 27. John Shergold. Middle row: 28. Frank Habets. 29. Allison Palmer. 30. Gerd Geyer. 31. Roger Kaesler. 32. Gene Hunt. 33. DeDe (Diane) Dawson. 34. Brian Pratt. 35. David L. Bruton. 36. Fred Collier. 37. Doug Boyce. 38. ?Bruce Lieberman. 39. Brenda Miles. 40. Suraj Kumar Parcha. 41. Catherine Cronier. ?42. 43. Jonathan Adrian. 44. Gregory Edgecombe. 45.? Loren Smith. 46? 47. Bryan Levman. 48. Mark Peterson. Front row: 49. Kevin Brett, 50. Jeong Gu Lee. 51. Raimund Feist. 52. Robert Owens. 53. Rodolfo Gozalo. 54. Gerald Kloc. 55 Gian Luigi Pillola. 56. Shanchi Peng. 57. Alan Thomas. 58. Niles Elderidge. 59. Arne Nilesen. 60. Kristina M
ansson, 61. Euan Clarkson. 62. Tom Whitely. 63. Dong-Chan Lee. 64. Duck Choi. At least eight persons on the programme lecture list have not been recognized. Photograph: Dave Rudkin who together with Helje P€arnaste, kindly produced the identification list.

organized with the aid of NATO money meant that no Soviet palaeontologists attended. However, we were especially fortunate in having Ladislav  Marek from Czeckoslovakia and Halszka Osmolska and Ewa Tomczykowa from Poland. These were the only two women working with trilobites who participated at the meeting, but this changed markedly at future meetings.

Brock University, St. Catharines, Ontario, Canada 1997 (August 22–25) This conference which became known by its title ‘Trilobite paleobiology: Past, present and future’ was a North American initiative alone, and the

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Fig. 6. St. Catharines, 1997: Pre-conference excursion to south central Ontario. Standing, from the left: Richard Fortey, Hans-Hartmut Krueger, Ingrid Krueger, Derek Siveter, Kristina M
ansson, Margaret Campbell, Robert Owens, Ronald Garney, Mark Peterson, Doug Boyce, Alan Thomas and Gian Luigi Pillola. Kneeling: Kevin Brett (co-leader), Dave Rudkin (co-leader), Helje P€arnaste and Derek Armstrong (adjunct leader). Nine participants had left when this picture was taken. Photograph: Dave Rudkin.

Fig. 7. Oxford 2001: Jonathan Adrain and Harry Whittington in deep conversation. Photograph: Helje P€arnaste.

committee was chaired by Steve Westrop. As the photographs (Figs 4–6) show, this was a most popular and well-attended meeting. For me, this was a chance to meet a large number of those who were only names to me until then. Many made up the organizing committee which included Jonathan Adrian, Brian Chatterton, Greg Edgecombe, Nigel Hughes, Ed Landing, Rolf Ludvigsen, Brian Pratt, Kevin Brett and Dave Rudkin. Rolf will be remembered for editing the trilobite newsletter after me. I remember an entertaining speech by Nigel Hughes who also sang for us at the dinner, and I had the pleasure of meeting up again with Ron Tripp. Ron was one of many gifted British amateur palaeontologists. He had left Britain long after retirement and was the living in Canada with

Fig. 8. Oxford 2001: Derek Siveter and Fred Shaw. Photograph: Helje P€arnaste.

his second wife. I also met up with Bill Fritz who had been a camp leader at Burgess almost 10 years to the day. In fact, I returned to Burgess with my wife after the meeting was over.

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Fig. 9. Oxford 2001: From the left, Peter Jell, Mrs. Jell, Nigel Hughes and Peng Shanchi. Photograph: Helje P€arnaste.

Fig. 11. Oxford 2001: Excursion to Wren’s Nest in the rain. Winfried Haas in pink poncho. Photograph: Helje P€arnaste.

Fig. 10. Oxford 2001: Alberto Simonetta and Winfried Hass at the conference reception, Oxford Museum. Photograph: D.L. Bruton.

Three ambitious field trips were held to the Avalon Terrane (led by Landing and Westrop), the Canadian Rocky Mountains (led by Chatterton and Pratt) and Ordovician stratigraphy and trilobite faunas of south central Ontario (led by Brett and Rudkin; Fig. 6). The aim of this meeting covered a broad range of then current interests (as now) in the relationship between Cambrian and post-Cambrian clades, the Ordovician radiation of trilobites, what relation there is between the arthropods from the Burgess Shale and a cladistic analysis of Cambrian arachnomorphs. A note from the meeting was later published by Adrain & Westrop (1999a) as a forward to a valuable selection of papers that they edited from the conference (Adrain & Westrop 1999b). As they indicated (Adrain & Westrop 1999a), there had been a long gap since the Oslo meeting; happily, the meetings after that at St. Catharines have been at much shorter intervals.

Fig. 12. Oxford 2001: Excursion to Wren’s Nest. From the left: Zhou Zhiyi, Bob Owens, Keith Ingham, Alan Thomas. Photograph: Helje P€arnaste.

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Fig. 13. Oxford 2001. The conference dinner at St John’s College. The author’s speech of thanks at the high table, but what was so amusing? From the left: David Bruton, Derek Siveter, Richard Fortey, Alan Owen and Dick Robison. Photograph: Helje P€arnaste.

Fig. 15. Toledo 2008: Pre-conference excursion. Giant asaphid trilobites at the Canelas quarry, Arouca, northern Portugal. Juan Carlos Gutierrez-Marco and Euan Clarkson for scale. Photograph: D.L. Bruton.

University of Oxford, England, 2001 (April 3–6) Fig. 14. Toledo 2008: Group photograph. Photograph through the courtesy of Helje P€arnaste.

The title of this meeting was ‘Trilobites and their relatives’ and was organized by a team led by Derek Siveter. It was well supported with a participation of

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Fig. 16. Toledo 2008: Mid-conference excursion. A relief for some of the participants, having transport by tractor and trailer. Photograph: D.L. Bruton

Fig. 17. Toledo 2008: Mid-conference excursion. Lunchtime entertainment with some conference participants showing their prowess at dancing the tango. Photograph: D.L. Bruton.

over 120 from 20 nations including Russia, Korea and China. The themes discussed were much the same as previous meetings and included functional morphology, evolution and palaeogeography and broader aspects of arthropod phylogeny. Proceedings from the meeting later appeared in a handsome publication dedicated to Harry Whittington (Lane et al. 2003).

This was the last meeting Harry attended (Fig. 7). He was then 85 but this did not prevent him travelling to Japan later in 2001 to receive the prestigious Emperor of Japan’s International Biology Prize. The Oxford meeting brought together many old friends (Figs 7–10). It was held at Eastertime and coincided with a most unfortunate outbreak of ‘foot and mouth’ disease that meant that walking in the

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Fig. 18. Prague 2012: Group photograph taken on steps outside the meeting venue, July 3. Key to photograph: 1. Michael Zwanzig. 2. Klaus M. Weber. 3. Yuta Shiino. 4. Yutaro Suzuki. 5. Derek E.G. Briggs. 6. Ian R. Gilbert. 7. Robert Sensenstein. 8. Benedicte van Lidth. 9. Kristina M
ansson. 10. Robert Johnson 11. Stĕpan Rak. 12. Martina Nohejlova. 13. Martina Aubrechtova. 14. Tomas Weiner. 15. Martin David. 16. Paul Hille. 17. Jorge Esteve. 18. John Paterson. 19. Brigitte Schoenemann. 20. Lukas Lajbl. 21. Mat
us Hyzny. 22. Hedvika Poukarova. 23. Simona Horychova. 24. David Holloway. 25. Allison C. Daley. 26. Phil Lane. 27. Fred C. Shaw. 28. Nigel Hughes. 29. David L. Bruton. 30. Juan Carlos Gutierrez-Marco. 31. Euan Clarkson. 32. Paul S. Hong. 33. Igor Korovnikov. 34. Petra Tonarova. 35. Brian Chatterton. 36. Elena Naimark. 37. Brenda Hunda. 38. Diego Garcia-Bellido. 39. Stewart J. Hollingworth. 40. Lee A. Hally. 41. Joe Collette. 42. Michal Mergl. 43. Richard A. Fortey. 44. Yumik Iwasaki. 45. Anastasiya Makorova. 46. Derek J. Siveter. 47. Paul A. Selden. 48. Helje P€arnaste. 49. Juan Antonio Vella Fernandez. 50. Mary Hollingworth. 51. Tatyana Pegel. 52. Petr Budil. 53. Oldrich Fatka. 54. James C. Lamsdell. 55. Martin Stein. 56. Javier Ortega Hernandez. 57. Stacey Gibb. 58. Marika Polechova. Photograph and naming of particpants courtesy of Oldrich Fatka and Helje P€arnaste.

countryside was forbidden and both pre- and postexcursions had to be cancelled. We did, however, enjoy a coach trip in pouring rain to the famous Silurian, Wren’s Nest, locality (Figs 11, 12) followed by a reception given by the Mayor of Dudley. The coat of arms of the city once included an outline of the ‘Dudley Bug’, Calymene blumenbachii, now, sadly, missing from the present-day coat of arms of more modern design. During the 1800s, limestone at Wren’s Nest was mined from the surface but later on, from

underground galleries and transported out by canal barges. We had the amusing experience of having to work our way into the ‘Dark Cavern’ with the sterling help of Diego Garcia-Bellido who, so-called, footed the barge using his feet on the tunnel roof while lying on his back. Historically, the Cavern, in 1839, was lit by gas for a lecture on geology by Sir Roderick Murchison for an audience of 15,000. The conference dinner was held in the impressive surroundings of the dining hall of St John’s College (Fig. 13).

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Fig. 19. Prague 2012: Lunchtime break, to celebrate David Bruton’s birthday on July 3rd. From the left: Richard Fortey, Derek Siveter, Derek Briggs, David Bruton, Paul Selden and Phil Lane. Photograph: Helje P€arnaste.

Fig. 20. Prague 2012: Mid-conference excursion on the deck of a Vltava River boat. Juan Carlos Gutierrez-Marco meets ‘Joachim Barrande (Petr Budil) opposite “Barrande’s Rock”’. Photograph: D.L. Bruton.

Toledo, Spain, 2008 (June 16–24) This meeting with the title ‘Trilo 08’ was well organized by Isabel Rabano and Juan Carlos GutierrezMarco with colleagues. Almost 100 participants took part in a meeting historically situated in the majestic city of Toldedo (Fig. 14). We were housed in various scattered hotels which many of us reached, suitcases clattering loudly over the cobbled streets, very late in the evening after a long drive from Arouca, northern Portugal. Here, under the excellent guidance of Artur Sa, we had seen the famous giant trilobites from Canelas during the pre-conference excursion (Fig. 15).

Fig. 21. Prague 2012: Mid-conference excursion on the deck of a Vltava River boat. Juan Carlos Gutierrez-Marco lifting Gian Luigi Pillola in a joyful attempt to throw him overboard. Photograph: D.L. Bruton.

In the quarry, we examined a newly uncovered bedding plane scattered with huge asaphid trilobites and then saw similar specimens on shale slabs that reached in height up to our waists. Lunch in the museum grounds was a memorable affair, and a monument had been erected to our visit inscribed with names in alphabetical order after first names. My wife Anne was embarrassed at being high on the list. In Arouca, we were also witness to the opening of the Geopark where Richard Fortey made a speech on our behalf and we walked to a roundabout in the nearby highway where there was a monument surmounted with a trilobite model.

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The meetings in Toledo were held in Real Fundaci on de Toledo (Museo Victorio Macho). The programme was the most ambitious, and 45 papers were presented along with numerous posters. In my view, this was trilobite research at its best with remarkable preservations shown on material from Bohemia, Morocco and Beecher’s Trilobite Bed in New York State. New methods combining sliced sections and 3D computer modelling emerged from work in the Hereford (Silurian) Lagerst€atte. A total of 75 short papers were published in time for the meeting (Rabano et al. 2008). Jonathan Adrian held a special session to demonstrate his global species database in preparation for

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15

the revised Treatise. We await, with interest, the successors to the first volume in the new series (Whittington et al. 1997). The mid-conference field trip on June 21 was devoted to the Ordovician trilobites and ichnofossils from the Toledo Mountains led by Juan Carlos Gutierrez-Marco. A beautifully illustrated field guide was produced by him and his wife, Isabel Rabano. The day was hot, and we oldies were grateful for the tractor and trailer ride to and from an outcrop (Fig. 16). We examined the Amorican quartzite and huge numbers of Cruziana. Slabs of these decorated the walls of a restaurant where we stopped for lunch. This was an extended affair with local dancers who encouraged the more athletic of us to try the tango (Fig. 17).

Prague, Czech Republic, 2012 (July 1–4)

Fig. 22. Prague 2012: Mid-conference excursion on the deck of a Vltava River boat. Two meeting stalwarts. Helje P€arnaste (left) and Kristina M
anson. Photograph: Anne Bruton.

This conference with title ‘On trilobites and their relatives’ was organized in Prague by Petr Budil and Oldrich Fatka. Over 90 participants from more than 20 countries were present at the conference (Fig. 18). Abstracts for 50 lectures were available (Budil & Fatka 2012) together with a field guide at mid-conference (Budil et al. 2012). Throughout the meeting, the emphasis was on trilobite morphology and systematics which was good to see when published (Budil et al. 2014). For me this was a sort of ‘homecoming’ having lived and studied in Prague in 1962. Things have

Fig. 23. Prague 2012. Post-conference excursion to Sardinia. Porto di Canalgrande. Back row from the left: Bernhard Schoenemann, Brigitte Schoenemann, John Paterson, Allison Daley, Samuel Zamora, Andrea Mancosu, Salvatore Vacca, Helje P€arnaste, Salvatore Noli. Middle row from the left: David L. Bruton, Lee-Ann Hally, Linda McCollum, Antonio Vela. Front row from the left: Anne Bruton, Gian Luigi Pillola, Luo Kunll. Photograph: Diego Garcia-Bellido.

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changed much since then, and it was a shame that the Narodni Museum was closed for refurbishment. While in Prague this time, I was able to celebrate my birthday with close friends (Fig. 19). The mid-conference excursion entailed a river cruise down the Vltava valley (Figs 20–22) past some of the classic geological sites such as Lentna Hill and the Branik rock as far as the famous Barrande’s Rock showing disharmonic folding of the Devonian succession. Joachim Barrande drew this locality several times during fieldwork, and here, our vessel stopped as we sipped champagne below the sign on the rock wall erected on 14 June 1884 in memory of Barrande. To our surprise, a figure dressed in clothes of the time appeared on deck: Petr Budil in the guise of Joachim Barrande himself (Fig. 20). Also on deck, Juan Carlos GutierrezMarco lifted up Gian Luigi Pillola in a playful attempt to cast him overboard (Fig. 21)! The day ended with a tram ride to the suburb of Barrandov and the village of Klukovice passing the picturesque sites in the Lower and Middle Devonian rocks before stopping in a woodland glade for a grilled sausage and salad lunch. At the Toledo meeting, as already mentioned, one of the excursions was held outside Spain, in Portugal, while the post-conference excursion in connection with the Prague meeting was held in Sardinia and organized by Gian Luigi Pillola from July 5 to 8 (Pillola 2012a,b). On separate days, we saw rocks and sections named for those who had worked on and described the faunas and stratigraphy. The coastal sections were most impressive with Lower Cambrian faunas in the Serra Scoris section near Gonnesa where we spent two nights. Later, we saw a Franco Rasetti locality at Porto di Canalgrande (Fig. 23) where the lunch stop was combined with a glorious swim in the clear sea. The last stop gave us the chance to meet Francesco Leone who took us to the type section of the Riu Is Arrus Member of the Monte Argentu Formation (Upper Ordovician) yielding exoskeletons of the nektaspid arthropod Tariccoia arrusensis. ‘Gigi’ was a wonderful guide and host. The heat was enervating as we left the capital Cagliari by train to the north of the island and flight home the following day from Olbia. Trilobite research has continued to blossom since the first conference in 1973, new research themes have emerged, and new problems have been identified. The conferences, including the very successful sixth meeting in Tallinn in 2017 organized by Helje

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P€arnaste, have provided a valuable and friendly opportunity for trilobite workers to gather, present new results and exchange ideas. I am sure that all will agree this must continue and I wish future organizers all the very best.

Acknowledgements I extend warm thanks to Hans Arne Nakrem and Karl Bruton for their help with photographs used here. Apart from my own collection, these have come from Helje P€arnaste, Dave Rudkin, Juan Carlos Gutierrez-Marco, Petr Budil and Gian Luigi Pillola. Each has helped to identify those present, together with Derek Siveter, Diego Garcia-Bellido and Nigel Hughes.

References Adrain, J.M. & Westrop, S.M. 1999a: Trilobite Paleobiology: Past, Present, and Future. Journal of Paleontology 73, 161–163. Adrain, J.M. & Westrop, S.M. (eds) 1999b: Papers from the Second International Trilobite Conference, August 1997. Journal of Paleontology 73, 161–371 Bruton, D.L. 2011: The Cambridge University-Geological Survey of Canada excavation of the Burgess Shale in 1967. Palaeontographica Canadiana 31, 9–18. Budil, P., Fatka, O. (eds) 2012: The 5th Conference on Trilobites and their Relatives. Abstracts. 59 pp. Czech Geological Survey & Charles University, Prague. Budil, P., Fatka, O. & Polechova, M. 2012: The 5th Conference on Trilobites and their Relatives. Mid-Conference Field Trip Guide. 15 pp. Czech Geological Survey & Charles University, Prague. Budil, P., Fatka, O., Holloway, D.J., Hughes, N. (eds). 2014: From J. Barrande to H.B. Whittington. Papers from The 5th Conference on Trilobites and their relatives. Bulletin of Geosciences 89, 201–450. Lane, P.D., Siveter, D.J., Fortey, R.A. (eds). 2003: Trilobites and their relatives. Contributions from the Third International Conference, Oxford 2001. Special Papers in Palaeontology 70, 1–397. Martinsson, A. (ed) 1975: Evolution and morphology of the Trilobita, Trilobitoidea and Merstomata. Fossils and Strata 4, 1–467. Pillola, G.L. 2012a: Geological outline of Sardinia, Italy: Historical overview of Sardinia. 5th Trilobite Conference 2012. Fieldtrip Guide-Book Sardinia 5–8 July 2012. Pillola, G.L. (ed.) 2012b: Three stops: Franco Rasetti day, Giuseppe Meneghini - Jan.Geog Bornemann day and Michele Taricco - Wolfgang Hammann day. 5th Trilobite Conference 2012. Fieldtrip Guide book, Sardinia 5–8 July 2012. Rabano, I., Gozalo, R., Garcıa-Bellido, D. (eds). 2008: Advances in trilobite research. Cuadernos del Museo Geominero, 9, Instituto Geol ogico y Minero de Espa~ na, Madrid, 448 pp. Whittington, H.B., Chatterton, B.D.E., Speyer, S.E., Fortey, R.A.F., Owens, R.M., Chang, W.-T., Dean, W.T., Jell, P.A., Laurie, J.R., Palmer, A.R., Repina, I.N., Rushton, A.W.A., Shergold, J.H., Clarkson, E.N.K., Wilmott, N.V. & Kelley, S.R.A. 1997: Treatise on Invertebrate Paleontology, Part O, Arthropoda 1, Trilobita (revised), volume 1. The Geological Society of America and University of Kansas Press, New York and Lawrence.

The 6th International Conference on Trilobites and their Relatives: Tallinn calling, Estonia celebrating € HELJE PARNASTE P€arnaste, H. 2019: The 6th International Conference on Trilobites and their Relatives: Tallinn calling, Estonia celebrating. Fossils and Strata, No. 64, pp. 17–22. The 6th International Conference on Trilobites and their Relatives was held in Tallinn, Estonia in July 2017. Estonian trilobites have long been known worldwide especially through the works of Karl Eduard von Eichwald, Carl Friedrich Schmidt, Armin Alek€ sander Opik, Valdar Jaanusson, Harry Mutvei, Reet M€annil and others. Estonia was thus an ideal location for this gathering. The goal of the conference was to present recent progress in studies on all aspects of trilobites and their relatives. More than 80 participants from 20 countries took part. The associated field excursions were inspired by the footsteps of Friedrich Schmidt who, in 1897, led a field excursion in Estonia organized for the International Geological Congress held in St. Petersburg. □ 6th Conference on Trilobites and their Relatives, Arthropoda, Estonia, Schmidt, Tallinn, Trilobita. Helje P€arnaste [[email protected]], Kivion NGO, P€aevalille 15-40 13517 Tallinn, Estonia; manuscript received on 2/06/2018; manuscript accepted on 6/07/2018.

The 6th International Conference on Trilobites and their Relatives was held in Tallinn, the capital of Estonia from 7 July 2017 to 10 July 2017. Estonia is celebrating its centenary as an independent country but the first descriptions of Estonian trilobites were published almost two centuries ago in 1825, by Baltic German geologist, physician and naturalist Karl Eduard von Eichwald (1795–1876). The basic knowledge of the majority of Estonian trilobites, with detailed descriptions and comparison with other regions of the world, was provided by Carl Friedrich Schmidt (1832–1908) in a series of monographs published between 1881 and 1907 (see also Bruton et al. 1997; Schmidt 1881, 1885, 1888, 1894, 1897, 1898, € 1901, 1904, 1906, 1907). Armin Aleksander Opik (1898–1983) refined the picture on the trilobites from the Ordovician System (1925–1930, 1937) before he had to escape from World War II to live in Australia where he became one of the most productive trilobite researchers of his time, describing over 300 species (Shergold 1985). Another trilobite specialist, Valdar Jaanusson (1923–1999) also escaped to Sweden as did Harry Mutvei (b. 1925) who has shed considerable light on ultrastructure of trilobite and other arthropod cuticles (e.g. 1974, 1977, 1981; Dalingwater et al. 1991). Schmidt’s descriptions were extremely long and detailed, very useful for later recognition of his taxa, while Swedish taxonomic descriptions of that time were rather short and commonly lacking in detail. Jaanusson brought some clarity to the issue and revised the asaphid (Jaanusson 1953a; 1953b) and illaenid (Jaanusson 1954,

1957) trilobites with a more modern approach. He showed changes in position and size of the eyes during growth, emphasizing aspects of these taxonomically important characters, and he paid attention to the details on the ventral side of the exoskeleton, in particular the attachment of the hypostome. Reet M€annil (1931–2005) refined our knowledge of Silurian taxa and also documented variants of their body plan depending on facies/depth (e.g. 1986, 1992). Ecological aspects were also pursued by Helje P€arnaste with various research teams in studying the Hirnantian faunas of Baltica (Popp & P€arnaste 2011; Hints et al. 2012; Ebbestad et al. 2015), Early to Middle Ordovician Baltic trilobites in comparison with those in Urals and China (Bergstr€om et al. 2013; P€arnaste & Bergstr€om 2013, 2014; P€arnaste et al. 2013), and the distribution of Baltoscandian proetids (P€arnaste et al. 2009; P€arnaste & Popp 2011; Popp & P€arnaste 2011). Further investigations of the earliest representatives of the Cheirurina (P€arnaste 2003; 2006a; 2006b) are in preparation, and work on Early Cambrian trilobites has recently been published (Schoenemann et al. 2017). With its long history of trilobite research, Estonia was an excellent candidate to host the trilobite conference and as the latest member of the succession of Estonian trilobite workers, I gladly organized it. The goal of the conference was to present recent progress in studies on all aspects of trilobites and their relatives. More than 80 participants from 20 countries took part (Fig. 1). Amateur collectors were

DOI 10.1002/9781119564232 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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FOSSILS AND STRATA

Fig. 1. Conference group photograph taken in the Tallinn Song Festival Grounds at the end of the mid-conference excursion. Standing (from the left): S. Losso, C. Cr^ onier, P. Budil, L. Laibl, R. Sensenstein, D. Siveter, M.A. Siveter, S. Pereira, D. Holloway, L. Holmer, G.L. Pillola, Z-L. Zhang, B. Schoenemann, B. Schoenemann, D. Briggs, C. Stocker, S. Pates, G. Geyer, B. Chatterton, P. Ahlberg, M. Zwanzig, J. Esteve, A. _ nska, F. Perez-Peris, A. Thomas, P. Selden, M. Selden, N. Hughes, S. Lei, S. Peng, J. Ortega-Hernandez, R. Johnson, B. Pratt, K. M Zyli ansson, R. Fortey, R. Birch; sitting (from the left): D. Bruton, A. Bruton, J. Fortey, E. Czanyo, J.C. Gutierrez-Marco, A. McIntyre, K. Brett, G. Brett, A. Brodskii, M. Kurth, H. Drage, Z-F. Zhang, L. McCobb, J-B. Hou, N. Machida, Ariuntogos M., S-B. Lee, J. Nowicki, M. Cyrulska-Nowicka, P. Hong, H. P€arnaste, A. Weug, M. Ghobadi Pour, L. Popov, A. Owen, S. Wernette, G. Owen, E. Tamm, S. Thomas, J. Briggs, M. Shaw, M. Johnson, M. Hopkins. (Photograph by H. P€arnaste).

Fig. 2. The participants on the 1897 field excursion led by Friedrich Schmidt gathered in front of the ruins of Tartu Cathedral which was renovated partly to house the University Library at that time. Standing (from the left): N.I. Kuznetsov, Ph. Lake, J. Wysogorski, Fr.von Huene, C. Gagel, A. Mickwitz, W. Rosenberg, J.P.J. Rawn, E. Stolley, unknown 1, unknown 2, F.T. Levinson-Lessing. People sitting are N. Andrussov, A. Rothpletz, J. Lemberg, H.G. Seeley, Fr. Schmidt, A. Remele, L. T€ ornquist, A. Andre, G. Holm, F. Gebauer, W. Deecke, C. Gottsche, and lying on the ground are: F.A. Bather, P. Bamberg, unknown 3 (candidates for unknown persons: Prof J.P. Felix, Prof T.M. Hughes, Prof C. Malaise and Colonel Schewyrew). (Photograph No VN07-23 in Estonian geocollections database http://geocollections.inf o/image/28818).

FOSSILS AND STRATA

6th Conference on Trilobites and their Relatives

19

€ Fig. 3. Pre-conference field-trip participants in front of the Armin Opik’s childhood house in Lontova village, Kunda. Standing (from the _ nska, D. Holleft): D. Bruton, S. Lei, S. Peng, J. Adrain, J. Ortega-Hernandez, B. Chatterton, M. Kurth, R. Birch, B. Schoenemann, A. Zyli loway, B. Schoenemann, A. McIntyre, S. Pates, G. Geyer, A. Bruton, J-B. Hou, P. Hong, S-B. Lee, G.L. Pillola, N. Hughes, H. P€arnaste, A. Brodskii, A. Owen, A. Thomas, G. Owen, S. Thomas; crouching in front: X-J. Zhu, M. Hopkins, S. Wernette, H. Drage, N. Machida, B. Pratt, S. Pereira. (Photograph by H. P€arnaste).

also encouraged to participate especially as their input to the science has risen quickly in recent years with the development of social media channels allowing worldwide connection and the sharing of news and findings. The conference covered 55 oral and poster contributions split between the sessions on the following: (1) Lagerst€atten; (2) functional morphology; (3) the early evolution of arthropods; (4) the trilobite Treatise, systematics, phylogeny and ontogeny; (5) Cambrian trilobites; (6) the Great Ordovician Biodiversification Event, biostratigraphy, biofacies and ecology (under the auspices of IGCP 653); and 7) Devonian trilobites. Some of the papers arising from these sessions are published in this special volume of Fossils and Strata thanks to the kind support of the Lethaia Foundation. The pre-, mid- and post-conference field trips were inspired by the footsteps of Friedrich Schmidt who, in 1897, led a field excursion in Estonia (Fig. 2) in connection with the 7th International Geological Congress held in St. Petersburg (see https://archive. org/details/compterendudelav01inte).

The pre-conference field trip took us eastward from Tallinn to the Lower Cambrian outcrop with one of the earliest trilobite faunas in the world and to several localities through the Ordovician succession to examine the trilobite associations in near-shore temperate limestones. We also examined the extremely diverse fauna in the organic-rich Kukruse oil shale, and near equatorial Upper Ordovician and Lower Silurian reefs. Kunda, the hometown of Armin € Opik, was visited (Fig. 3) as was Tartu University, where most Estonian geologists receive their diploma € and where Opik’s trilobite collections were displayed for us by Mare Isakar at the Natural History Museum. The famous Kukruse Stage was investigated both above and below ground at the mining museum in Kohtla-N~omme, and one of the points on Struve’s Geodetic Arc was examined near the V~oivere windmill where information on the astronomer and geodesist Friedrich Georg Wilhelm Struve (1793–1864) was provided. The mid-conference field session, expertly led by Heikki Bauert and Jaak N~olvak, brought us to the

20

H. P€arnaste

FOSSILS AND STRATA

Fig. 4. Post-conference field-trip participants at Suurem~ oisa Mannor House on Hiiumaa island where Friedrich Schmidt hosted the excursion in 1897. From the left: B. Pratt, J. Fortey, R. Fortey, S. Pereira, M. Kurth, A. Brodskii, H. P€arnaste, M. Selden, P. Selden, M. Johnson, R. Johnson, N. Machida. (Photograph by H. P€arnaste).

Uuga locality of the Pakri Cliff in Paldiski next to the ruins of the Baltiiski Port built by Peter the Great in 1718. The 11 metres of Ordovician succession exposed here include Floian glauconite sandstones with a calcareous uppermost part preserving the earliest Ordovician trilobite fauna in Estonia (P€arnaste 2006b). This is followed by Dapingian limestones with monospecific megistaspid cemeteries and above these the earliest Estonian mudmounds with accumulations of Pliomera sclerites. The Darriwilian Stage starts here with Pakri Sandstone Formation rich in organics and a very diverse trilobite fauna (P€arnaste 2004) which is replaced by a new less € diverse fauna at the boundary of Oland and Viru regional series (P€arnaste & Bergstr€om 2013). The type locality for the Lower Cambrian Kakum€agi Member of the Tiskre Formation was visited in the Rocca al Mare Open Air Museum west of Tallinn and the excursion ended on the hillside where the Estonian Song Festival is held (Fig. 1) next to the Suhkrum€agi Cliff, famous for its trilobites. The post-conference field trip, west of Tallinn, took us to Upper Ordovician and Silurian localities on the mainland and on the popular tourist islands

of Hiiumaa and Saaremaa. We studied differences between trilobite associations of the late Ordovician and early Silurian reefs and saw low-diversity Silurian trilobite fauna of various facies types, and also eurypterids from their classical localities. Three impact craters (Neugrund, K€ardla and Kaali) provided a wider context to the geology in this part of Estonia. On Hiiumaa island, we stopped to see the manor house of Suurem~oisa (Fig. 4) where Schmidt and his companions were honoured in 1897; while on Saaremaa island, we visited the medieval castle of Kuressaare and the birth place of the great explorer Fabian Gottlieb Thaddeus von Bellingshausen (1778–1852) who discovered the continent of Antarctica.

Acknowledgements The members of the Organizing and Scientific Committee are thanked for their help and were as follows: Ethel Tamm – Estonian Museum of Natural History; Mare Isakar – Natural History Museum, University of Tartu, Estonia; Heikki Bauert and Jaak N~olvak – Institute of Geology, Tallinn University of

FOSSILS AND STRATA

6th Conference on Trilobites and their Relatives

Technology; Aivo Averin – IPT Projektijuhtimine € Estonia; Jonathan M. Adrain – The University OU, of Iowa, USA; Per Ahlberg – Lund University, Sweden; David L. Bruton – Natural History Museum, Oslo University, Norway; Brian D.E. Chatterton – University of Alberta, Edmonton, Canada; Catherine Cr^ onier – The Lille University of Science and Technology, France; Jan Ove R. Ebbestad – Museum of Evolution, Uppsala University, Sweden; Jorge Esteve – Complutense University of Madrid, Spain; David J. Holloway – Museums Victoria, Melbourne, Australia; Nigel C. Hughes – University of California, Riverside, USA; Lucy M.E. McCobb – National Museum Wales, UK; Javier Ortega-Hernandez – University of Cambridge, UK; Alan W. Owen – University of Glasgow, UK; Brian R. Pratt – Univer_ nska – sity of Saskatchewan, Canada; Anna Zyli University of Warsaw, Poland. I also thank following organizations for their financial support: The Lethaia Foundation, The Palaeontological Association, Kunda Nordic, Heidelberg Cement Group, IGCP € and private backers. I am also very 653, Lossikivi OU grateful to my good friend Tiina K~ore and my parents Helgi and Heinar L~ohmus for their support and encouragement.

Jaanusson, V. 1957: Unterordovizische Illaeniden aus Skandinavien. Bulletin of the Geological Institutions of the University of Uppsala 37, 79–165. M€annil, R. 1986: Distribution of trilobites in different facies of the east Baltic Silurian. In Kaljo, D. & Klaamann, E. (eds): Theory and Practice of Ecostratigraphy, 99–109. Valgus, Tallinn. (In Russian, English summary). M€annil, R. 1992: Trilobite faunal changes in the East Baltic Silurian. Proceedings of the Estonian Academy of Sciences, Geology 41, 198–204. Mutvei, H. 1974: SEM Studies on Arthropod Exoskeletons. Part 1: Decapod Crustaceans, Homarus gammarus L. and Carcinus maenas (L.). Bulletin of the Geological Institutions of the University of Uppsala N.S. 4, 73–80. Mutvei, H. 1977: SEM Studies on Arthropod Exoskeletons. Part 2: Horseshoe crab Limulus polyphemus (L.) in comparison with extinct eurypterids and recent scorpions. Zoologica Scripta 6, 203–213. Mutvei, H. 1981: Exoskeletal structure in the Ordovician trilobite Flexicalymene. Lethaia 14, 225–234. € Opik, A.A. 1925: Beitr€age zur Kenntnis der Kukruse- (C2-) Stufe in Eesti, I. Acta Commentationes Universitatis Dorpatensis A 8, 1–18, pls 1–2. € Opik, A.A. 1927: Beitr€age zur Kenntnis der Kukruse- (C2- C3-) Stufe in Eesti, II. Acta Commentationes Universitatis Dorpatensis A 12, 1–35, pls 1–6. € Opik, A.A. 1928: Beitr€age zur Kenntnis der Kukruse-(C2-) Stufe in Eesti III. Acta et Commentationes Universitatis Tartuensis A 13, 1–42, pls 1–4. € Opik, A.A. 1930: Beitr€age zur Kenntnis der Kukruse- (C2-C3-) Stufe in Eesti, IV. Acta et Commentationes Universitatis Tartuensis A 19, 1–34, pls 1–6. € Opik, A.A. 1937: Trilobiten aus Estland. Acta et Commentationes Universitatis Tartuensis A 32, 1–163, pls 1–26. P€arnaste, H. 2003: The Lower Ordovician trilobite Krattaspis: the earliest cyrtometopinid (Cheiruridae) from the Arenig of the East Baltic. Special Papers in Palaeontology 70, 241–257. P€arnaste, H. 2004: Revision of the Ordovician cheirurid trilobite genus Reraspis with the description of the earliest representative. Proceedings of the Estonian Academy of Sciences, Geology 53, 125–138. P€arnaste, H. 2006a: The earliest encrinurid trilobites from the east Baltic and their taxonomic interest. Palaeontology 49, 155–170. P€arnaste, H. 2006b: Proceedings of the Estonian Academy of Sciences, Geology 55, 109–127. P€arnaste, H. & Bergstr€ om, J. 2013: The asaphid trilobite fauna: Its rise and fall in Baltica. Palaeogeography, Palaeoclimatology, Palaeoecology 389, 64–77. P€arnaste, H. & Bergstr€ om, J. 2014: Bulletin of Geosciences 89, 431–450. P€arnaste, H. & Popp, A. 2011: First record of Telephina (Trilobita) from the Ordovician of northeastern Estonia and its stratigraphical implications. Estonian Journal of Earth Sciences 60, 83–90. P€arnaste, H., Popp, A. & Owens, R.M. 2009: Distribution of the order Proetida (Trilobita) in Baltoscandian Ordovician strata. Estonian Journal of Earth Sciences 58, 10–23. P€arnaste, H., Bergstr€ om, J. & Zhou, Z.-Y. 2013: High resolution € trilobite stratigraphy of the Lower-Middle Ordovician Oland Series of Baltoscandia. Geological Magazine 150, 509–518. Popp, A. & P€arnaste, H. 2011: Biometry and life style of the Ordovician proetide trilobite Cyamella stensioei Owens, 1979. GFF 133, 111–123. Schmidt, F. 1881: Revision der ostbaltischen Trilobiten. Abtheilung I: Phacopiden, Cheiruriden und Encrinuriden. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VII 30, 1–237, pls 1–16. Schmidt, F. 1885: Revision der ostbaltischen Trilobiten. Abtheilung II: Acidaspiden und Lichiden. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VII 33, 1–127, pls 1–6. € Schmidt, F. 1888: Uber eine neuentdeckte undercambrische fauna in Estland. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VII 36, 1–27, pls 1–2.

References Bergstr€om, J., P€arnaste, H. & Zhou, Z.-Y. 2013: Trilobites € and biofacies in the Ordovician Oland Series (Tremadocian–mid Darriwilian) of Baltica and a brief comparison with the Yangtze Plate. Estonian Journal of Earth Sciences 62, 205–230. Bruton, D.L., Hoel, O.A., Beyene, L.T. & Ivantsov, A.Y. 1997: Catalogue of the trilobites figured in Friedrich Schmidt’s ‘Revision der ostbaltischen silurischen Trilobiten’ (1881–1907). In Contributions from the Palaeontological Museum, volume 403, 117 pp. University of Oslo, Oslo. Dalingwater, J.E., Hutchinson, S.J., Mutvei, H. & Siveter, D.J. 1991: Cuticular ultrastructure of the trilobite Ellipsocephalus € polytomus from the Middle Cambrian of Oland, Sweden. Palaeontology 34, 205–217. Ebbestad, J.O.R., H€ ogstr€ om, A.E.S., Frisk,  A.M., Martma, T., Kaljo, D., Kr€oger, B. & P€arnaste, H. 2015: Terminal Ordovician stratigraphy of the Siljan district, Sweden. GFF 137, 36–56. von Eichwald, J.K.E. 1825: Geognostico-zoologicae per Ingriam marisque Baltici provincias nec non de Trilobitis observationes. 58 pp. Casani. Hints, L., P€arnaste, H. & Gailite, L.-I. 2012: Hirnantia sagittifera (Brachiopoda) and Mucronaspis mucronata s.l. (Trilobita) in the Upper Ordovician of the East Baltic: taxonomy and distribution. Estonian Journal of Earth Sciences 61, 65–81. €ber baltoskandische Jaanusson, V. 1953a: Untersuchungen u Asaphiden I. Revision der mittelordovizischen Asaphiden des Siljan-Gebietes in Dalarna. Arkiv F€or Mineralogi och Geologi 1, 377–464, pls 1–10. €ber baltoskandische Jaanusson, V. 1953b: Untersuchungen u Asaphiden II. Revision der Asaphus (Neoasaphus)-Arten aus dem Geschiebe des s€ udbottnischen Gebietes. Arkiv F€or Mineralogi och Geologi 1, 465–499, pls 1–6. Jaanusson, V. 1954: Zur Morphologie und Taxonomie der Illaeniden. Arkiv F€or Mineralogi och Geologi 1, 545–583, pls 1–3.

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Schmidt, F. 1894: Revision der ostbaltischen Trilobiten. Abtheilung IV: Calymeniden, Proetiden, Bronteiden, Harpediden, Trinucleiden, Remopleuriden und Agnostiden. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VII 42, 1– 93, pls 1–6. Schmidt, F. 1897: Excursion durch Estland, 22 pp. Stassulewitsch, St. Petersburg. Schmidt, F. 1898: Revision der ostbaltischen Trilobiten. Abtheilung V: Asaphiden. Leif 1. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VIII 6, 1–46. Schmidt, F. 1901: Revision der ostbaltischen Trilobiten. Abtheilung V: Asaphiden. Leif 2. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VIII 12, 1–113, pls 1–12. Schmidt, F. 1904: Revision der ostbaltischen Trilobiten. Abtheilung V: Asaphiden. Leif 3. Memoires de l’Academie

FOSSILS AND STRATA Imperiale des Sciences de St-Petersbourg VIII 14, 1–68, pls 1–8. Schmidt, F. 1906: Revision der ostbaltischen Trilobiten. Abtheilung V: Asaphiden. Leif 4. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VIII 19, 1–63, pls 1–8. Schmidt, F. 1907: Revision der ostbaltischen Trilobiten. Abthei€ mit Nachtr€agen und lung VI: Allgemeine Ubersicht Verbesserungen. Memoires de l’Academie Imperiale des Sciences de St-Petersbourg VIII 20, 1–104, pls 1–3. Schoenemann, B., P€arnaste, H. & Clarkson, E.N.K. 2017: Structure and function of a compound eye, more than half a billion years old. PNAS 114, 13489–13494. € Shergold, J.H. 1985: Armin Aleksander Opik (1898–1983). BMR Journal of Australian Geology & Geophysics 9, 69–81.

Early post-embryonic trilobite stages and possible eggs from the ‘T
unel Ordov
ıcico del Fabar’ (Middle Ordovician, northwestern Spain)

S LAIBL, ISABEL RABANO
ENRIQUE BERNARDEZ, JORGE ESTEVE, LUKA AND JUAN CARLOS
GUTIERREZ-MARCO Bern
ardez, E., Esteve, J., Laibl, L., R
abano, I. & Guti
errez-Marco, J. C. 2019: Early postembryonic trilobite stages and possible eggs from the ‘T
unel Ordov
ıcico del Fabar’ (Middle Ordovician, northwestern Spain). Fossils and Strata, No. 64, pp. 23–33. The sub-surface section of the Middle Ordovician Sueve Formation of the Cantabrian Zone, studied during the construction of a tunnel in the A-8 free highway of northern Spain, provided abundant fossiliferous horizons rich in trilobites of Darriwilian age. Finegrained mudstones of the Cofi~ no Member delicately preserve a number of early stages of the calymenacean trilobite Prionocheilus mendax (Vanek), from protaspides to meraspid degree 2, including in situ exuviae with disarticulated librigenae. From the upper part of the Bayo Member, small clusters of pyrite spheres ca. 0.5 mm in diameter are recorded, and may represent eggs of trilobites, being associated with the pliomerid Placoparia (Coplacoparia) tournemini. (Rouault) in the same beds. The sphaeroids may represent the pyrite infilling of the internal cavity of possible eggs, and the covering is replaced by phyllosilicates. Differences in shape and size from presumed olenid eggs may be caused by the particular environmental adaptations of the latter group. The relatively large size of both the calymenid larvae and the pyritized eggs suggests a lecithotrophy development related to higher latitudes and/or with scarce organic matter. □ Development, fossil eggs, Gondwana, lecithotrophy, Spain, trilobites. Enrique Bern
ardez [[email protected]], Departamento de Geolog
ıa, Universidad de Atacama, Avenida Copayapu 485, Copiap
o, Atacama, Chile; Jorge Esteve [[email protected]], Departamento de Geociencias, Universidad de los Andes, Cra 1 No 18A-10 AA 4976 Bogot
a DC, Colombia; Luk
as Laibl [[email protected]], Institute of Geology, The Czech Academy of Sciences, Rozvojov
a 269, 165 00 Prague 6, Czech Republic; Institute of Earth Sciences, University of Lausanne, 1015 Lausanne, Switzerland; Isabel R
abano [[email protected]], Instituto Geol
ogico y Minero de Espa~ na, R
ıos Rosas 23, 28003 Madrid, Spain; Juan Carlos Guti
errez-Marco [[email protected]], Instituto de Geociencias (CSIC, UCM), Dr. Severo Ochoa 7 planta 4, 28040 Madrid, Spain; Departamento de Geodin
amica, Estratigraf
ıa y Paleontolog
ıa, Facultad CC, Geol
ogicas UCM, Jos
e Antonio Novais 12, 28040 Madrid, Spain; manuscript received on 28/11/2017; manuscript accepted on 1/05/2018.

Introduction Ordovician trilobites from the Mediterranean region, located during this period in high Gondwanan palaeolatitudes close to the South Pole (Torsvik & Cocks 2017), display a characteristic palaeobiogeographical signature related to their occurrence in shallow shelf facies, mostly dominated by siliciclastic sediments. The typical assemblages were originally named as the ‘Selenopeltis province’ (Whittington & Hughes 1972) and later designated as the ‘calymenacean–dalmanitacean’ shelf fauna (Cocks & Fortey 1988, 1990; Fortey & Cocks 2003). Within this South Gondwana palaeobiogeographical region, a great number of trilobite taxa have been described from the Ordovician of southwestern Europe (e.g. Dean 1966; Hammann 1974,

1976, 1983, 1992; Henry 1980; Romano 1980; R
abano 1990; Hammann & Leone 1997, 2007; Pereira et al. 2015). Nevertheless, within the extensive palaeontological literature available, details of the early postembryonic development of trilobites have rarely been documented. So far, the late meraspid stages have been described for the pliomerids Placoparia (Coplacoparia) borni Hammann (Hammann 1974, pl. 10, figs 167– 170), Placoparia (Coplacoparia) tournemini (Rouault; R
abano 1989, pl. 26, fig. 10), Pateraspis mediterranea Hammann (Hammann 1974, pl. 11, fig. 180) and Eccoptochile almadenensis Romano (Romano 1980, pl. 79, fig. 5; R
abano 1989, pl. 28, fig. 7); the harpetid Eoharpes guichenensis Henry & Philippot (Henry 1980, pl. 2, fig. 4); and the calymenines Kerfornella miloni Henry (Henry 1980, pl. 22, fig. 9) and Colpocoryphe thorali conjugens Hammann. From the last of

DOI 10.1002/9781119564232 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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ardez et al.

these species, a single early meraspid specimen (degree 1) was illustrated by R
abano (1989, pl. 18, fig. 7). An explanation for the poor record of these early post-embryonic stages of Middle Ordovician trilobites in Ibero-Armorica may be the strong hydrodynamics of the sedimentary environments on the sea bottom, usually placed above the storm wave base, as well as the widespread record of relatively coarse sediments with a generalized absence of fine mudstones derived from quiet-water environments. Here, we describe a new find of protaspid and early meraspid stages from the widely distributed calymenine trilobite Prionocheilus mendax (Vanek, 1965), as well as some enigmatic sphaeroidal objects, now pyritized, associated with the pliomerid trilobite P. (Coplacoparia) tournemini (Rouault, 1847) and whose interpretation as possible eggs is considered.

Materials and methods The trilobite specimens examined in this study were collected from two different horizons within the tunnel, and are preserved as internal and external moulds in dark brown to greenish mudstones. Study of the surficial characters of their carapaces was made through latex casts taken from external moulds. Some of the illustrated specimens were whitened with MgO and photographed using a Canon EOS 5D digital camera with a Canon Compact-Macro 100 mm EF lens. Early developmental stages that needed greater magnification were mounted on SEM stubs, carbon-coated and imaged in a Jeol JSM 6010LA Plus scanning electron microscope, in the SEM laboratory of the Geological Survey of Spain (IGME, Tres Cantos, province of Madrid). Pyritized sphaeroids were studied and analysed using an ESEM Quanta 200 environmental scanning electron microscope with EDS and WDS, low vacuum operating at a voltage of HV 20 kV using secondary and retrodispersed electrons. This equipment belongs to the non-destructive technics analytical services of the National Museum of Natural Sciences (MNCN-CSIC, Madrid). The specimens are housed in the Museo Geominero (MGM) in Madrid. Figures were made by means of Adobe Photoshop CS6 Extended.

Geological setting The studied material comes from the Sueve Formation, a dark shale unit (50–100 m thick) with some intercalated siltstones and ironstones, which overlies the Barrios Formation in the Laviana–Sueve thrust sheet of the eastern Cantabrian Zone of the Iberian Massif (Fig. 1). The latter unit represents one of

FOSSILS AND STRATA

the most extensive and characteristic units of the Lower Palaeozoic regional succession (Aramburu & Garc
ıa-Ramos 1993), being in part equivalent to the Armorican Quartzite of other Ibero-Armorican areas (Guti
errez-Alonso et al. 2007), although in the Cantabrian Zone, the Floian beds are restricted to the uppermost part of the formation (Guti
errezAlonso et al. 2016). Modern lithostratigraphical and palaeontological studies of the Sueve Formation were presented by Guti
errez-Marco et al. (1996, 1999) based on the only available surface outcrops, which are very discontinuous. However, the excavation of a tunnel for the Cantabrian free Highway (A-8) in northern Spain, allowed a complete bed-by-bed study of the sub-surface section of the entire Sueve Formation (Guti
errez-Marco et al. 2003), that is still awaiting publication. However, preliminary data found in the tunnel were presented in a catalogue for an exhibition of rocks and fossils coming from the tunnel (Guti
errez-Marco & Bern
ardez 2003). The tunnel, later renamed as ‘T
unel Ordov
ıcico del Fabar’ due to the relevance of the scientific discoveries held in the Ordovician sequence, lies about 7 km west of the town of Ribadesella (Asturias region). From a geological point of view, the Laviana–Sueve thrust sheet penetrated by the tunnel represents an external zone of the Variscan Chain, located in the inner part of the Cantabrian–Asturian Arc (Pastor-Gal
an et al. 2011). The Sueve Formation in the tunnel section is about 85 m thick and comprises a lower member of very fossiliferous massive dark mudstones (Cerrac
ın Member, 12.8 m), followed by sandy siltstones with some thin intercalations of fine-grained sandstones and some shaly beds (Bayo Member, 33.4 m) and ending with dark siltstones and mudstones (Cofi~ no Member, 38.5 m). The base of the Sueve Formation bears an ooidal ironstone bed that in the past was an object of mining activity; a second ironstone is known in the upper part of the Bayo Member, but in this case it is a highly bioturbated sideritic layer, not ooidal in character. Among the abundant specimens of Middle Ordovician trilobites obtained from the tunnel section, the palaeontological sample TUN-055 was the only one – from a total of 116 fossiliferous beds sampled in the Sueve Formation in which larvae and early stages of development have been recorded. The extreme rarity of these is more surprising when considering the huge volume (up to dozens of cubic metres) and the unweathered character of the palaeontological samples yielded by the tunnel. TUN-055 is a special bed located near the base of the Cofi~ no Member, which offers several bedding plane concentrations of minute fossils such as ostracods (Marquezina, Quadritia), conodonts (Drepanoistodus, Panderodus and Semiacontiodus), machaeridians

FOSSILS AND STRATA

Trilobite juveniles and possible eggs from Spain

25

Fig. 1. A, Geological sketch map of the area between Caravia and Ribadesella (Asturias, northern Spain) showing vertically dipping outcrops of the Barrios and Sueve formations (Ordovician) in the northeastern ends of the Laviana (W) and Rioseco nappes, and the path of the A8 free highway, including the El Fabar tunnel (thick black line). The star indicates the tunnel section through the Sueve Formation. B, Stratigraphical column of the main units traversed by the tunnel, showing the position of the studied horizons in the Sueve Formation (TUN-055 and -057) as well as significant beds and fossils occurring in the Barrios Formation: 1, trilobites; 2, Cruziana (trace fossil); 3, Skolithos pipe rock; 4, phyllocarids; 5, organic-walled microfossils; 6, graptolites; and 7, lingulid shell bed. Members within the Sueve Formation are as follows: a, Cerrac
ın; b, Bayo; c, Cofi~ no; Or, Oretaniense; and Db. Dobrotiviense.

(Plumulites), cnidarians (Sphenothallus) and trilobites, including representatives of rare genera such as Dionide, Primaspis, Parabarrandia and Selenopeltis, as well as diverse trilobite post-embryonic stages (i.e. protaspid and meraspid stages of Prionocheilus) besides diverse holaspid forms of Isabelinia and Dionide not yet studied. The associated record of the graptolite Gymnograptus linnarssoni (Moberg) makes it possible to date this bed to the middle upper Darriwilian (= lower Dobrotivian in Guti
errez-Marco & Bern
ardez 2003). The other studied material comes from a bed 2.7 m below the former and of approximately the same chronostratigraphical age, but in this case situated near the top of the Bayo Member instead of the basal part of the Cofi~ no Member. This fossiliferous bed (TUN-057), composed of dark noduliferous mudstones, yielded eight trilobite genera, with some abundance of complete specimens of Placoparia, Neseuretus and Isabelinia, along with diverse bivalves,

gastropods, cephalopods, brachiopods, echinoderms, cnidarians, hyoliths, ostracods and graptolites. From this assemblage, minute clusters of sphaeroidal pyritized objects have been found, and their possible interpretation as trilobite eggs is discussed below.

Trilobite early stages The record of early post-embryonic stages of calymenacean trilobites from the ‘T
unel Ordov
ıcico del Fabar’ was briefly mentioned by Guti
errez-Marco & Bern
ardez (2003), but the material was never studied in detail. In the present work, the examined material is confidently assigned to P. mendax (Vanek, 1965), a species widely distributed in the Middle Ordovician (Darriwilian 2–3, see Bergstr€om et al. 2009) of Bohemia (Vanek 1965), southwestern Europe (Henry 1980; Romano 1980; Hammann 1983; R
abano 1989) and Great Britain (Kennedy 1989). Adult specimens

26

Bern
ardez et al.

of P. mendax (Fig. 2A) range in the section between 10.5 and 47.4 m above the base of the Sueve Formation, being more common near the top of the Cerrac
ın Member and in the transitional beds between the Bayo and Cofi~ no members. The assemblage of early stages of P. mendax recorded at the horizon TUN-055 (1 m above the base of the Cofi~ no Member) belongs to protaspid and meraspid periods (Fig. 3). The earliest recorded protaspid stage (n = 2) of the species is elliptical to elongate sub-hexagonal in outline, 1.08–1.04 mm long and 0.87–0.86 mm wide. The glabella is sub-rectangular in outline, comparatively large. The occipital ring bears a small node. The pre-ocular field is strongly inflated and relatively wide, ca. 22% of the glabellar length. The fixigenae are comparatively narrow, 28% of the glabellar length. The specimen illustrated on Figure 3A and 3E seems to have a palpebral lobe located laterally. The trunk is composed of three segments plus a terminal piece that tapers posteriorly. The division between protocranidium and trunk is evident only in axial part, and no distinct transverse line separating these parts is visible in the pleural part of the exoskeleton. Calymenine trilobites usually have one or two planktonic stages (designated by Chatterton et al. 1990 as P1 and P2), that are followed by two benthonic stages (B1 and B2 sensu Chatterton et al.

FOSSILS AND STRATA

1990). However, some calymenine lineages such as Homalonotidae seem to lack planktonic stages (see Lu & Wu 1982; Chatterton et al. 1990). Based on the comparison with other Calymenina, we suggest that protaspides of P. mendax might be homologous to the first benthonic stage (B1). This assumption is based mainly on the following characters: (1) the absence of medial furrow crossing L1 and L2 that is characteristic for all planktonic calymenine protaspides (see Chatterton et al. 1990; Edgecombe et al. 1998; Lerosey-Aubril 2007); (2) the absence of a distinct transverse furrow separating protocranidium and trunk that is often present in B2 but less distinct in B1 (see Chatterton et al. 1990; Edgecombe et al. 1998); and (3) number of post-cephalic segments – B1 seems to have about three segments while B2 usually have more (Chatterton et al. 1990). The known meraspid larvae (n = 3) of P. mendax are slightly elliptical in outline, 1.8–2.2 mm long and 1.6–1.7 mm wide. The cranidium is semicircular to sub-trapezoidal in outline. The glabella tapers gently anteriorly. The facial suture seems to be proparian. The palpebral lobes are located anterolaterally. The librigena is triangular in shape bearing tiny spines along the margin (Fig. 3C). The thorax is composed of two tergites (making this meraspid degree 2) and has an axis of high convexity, well defined by deep axial furrows; the axial ring of T2 is narrower (tr.) than that of T1. The pleurae are moderately flat,

Fig. 2. A, Internal mould of Prionocheilus mendax (Vanek, 1965) from TUN-097 Cofi~ no Member, upper Darriwilian (MGM-2554O). B, Internal mould of Placoparia (Coplacoparia) tournemini (Rouault, 1847) with abraded pygidium from the sample TUN-057 (MGM2560O). Scale bars = 5 mm (A) and 10 mm (B).

FOSSILS AND STRATA

Trilobite juveniles and possible eggs from Spain

27

Fig. 3. Post-embryonic stages of Prionocheilus mendax (Vanek, 1965) from the sample TUN-55, Cofi~ no Member, upper Darriwilian. A, E, Internal mould and latex cast of the first benthonic stage, B1 sensu Chatterton et al. 1990 (MGM-2795O-1). B, F, Internal mould and latex cast of the first benthonic stage, B1 sensu Chatterton et al. 1990 (MGM-2795O-2). C, Internal mould of a meraspid degree 2, note disarticulated free cheek bearing tiny spines along the margin (MGM-2800Oa-1). D, Internal mould of a meraspid degree 2, with disarticulated pygidium (MGM-2800Oa-2). G, H, Latex cast and internal mould of a meraspid degree 2 (MGM-2800Ob-3). Scale bars = 1 mm (C, D, H), 0.5 mm (A, B, G) and 0.2 mm (E, F).

becoming slightly shorter (exsag.) and narrower (tr.) from T1 to T2. The meraspid pygidium is relatively large, ca 35% of the exoskeleton, semi-elliptical in outline, with anterior margin extending posterolaterally and posterior margin concave medially, Wshaped in outline. Axis convex, divided into six segments and a terminal piece (Fig. 3C, G, H). Pleural field convex with distinct pleural and interpleural furrows.

Possible trilobite eggs Placoparia (Coplacoparia) tournemini (Rouault, 1847) is one of the most abundant pliomerid trilobites in the Sueve Formation, being represented by numerous complete exoskeletons (Fig. 2B) and also by clusters of juvenile specimens (either prone or enrolled) of up to 20 individuals in the sample TUN057. Associated with these trilobites in the same bed, clusters of small sphaeroidal objects, preserved in unweathered pyrite with its characteristic shine and colour under natural light, are recorded (Fig. 4). They do not show any evidence of current alignment or resedimentation on the bedding planes. Pyritization also occurs in some graptolites, from the Bayo Member, with preservation of the internal moulds of

biserial rhabdosomes with their original relief, and even preserving details of the fusellar rings of the thecae (Guti
errez-Marco & Bern
ardez 2003, figs, pp. 290–291). Significantly, pyritization did not affect other fossil groups in the sample TUN-057, where pyritic nodules and aggregates of framboidal or disseminated pyrite are absent. According to the morphology and distribution pattern on bedding planes, these sphaeroids seem to be pre-diagenetic, corresponding to organic structures quickly pyritized after the initial burial. The sphaeroids, with a mean diameter of 0.5 mm, are surrounded by a thin layer made of phyllosilicates (sericite: arrowed in Fig. 4D) with their main planes sub-perpendicular to the sphaeroid surface. This phyllosilicate layer may be interpreted as the infill of a void originally occupied by an organic envelope. The surface of the pyritic sphaeroids shows a polygonal (mainly sub-hexagonal) pattern which in some cases is densely packed, whereas in others, the crystalline growth is not complete, showing polygonal bodies (ca. 25 μm in diameter) separated by phyllosilicates (Fig. 4E). In a slightly broken specimen (Fig. 4G–H), very small pyritic sphaeroids can be observed in a section perpendicular to the main surface, along with an octahedral pyrite crystal of a later generation. Fracturing of this specimen seems

28

Bern
ardez et al.

FOSSILS AND STRATA

Fig. 4. Possible trilobite eggs from the sample TUN-057, Darriwilian of northern Spain (MGM-8111O). A–C, cluster photographed under natural light showing pyrite shine (A), coated with MgO (B) and in ESEM image using retrodispersed electrons (C). D, Upper left sphaeroid of cluster shown in A–C, showing the outer phyllosilicate envelope (arrowed). E, Detail of polygonal pattern on the surface of a sphaeroid indicating incomplete crystalline growth. F, Two sphaeroids, the left one showing a fracture. G, H, Detail of sphaeroid on left hand side of F with aggregates of pyrite framboids and a octahedral pyrite crystal (at the bottom of H) seen in the fracture. I, Cluster of enrolled specimens of Placoparia (Coplacoparia) tournemini (Rouault) from bed TUN-057, (MGM-2564O). Figures E–H were taken using an environmental SEM in the National Museum of Natural Sciences, Madrid. Scale bars = 10 mm (A–C), 5 mm (F, I), 100 μm (D, G) and 50 μm (E, H).

to have been caused by compaction in an early diagenetic stage, when the sphaeroid was incipiently pyritized. The pyritization, restricted to the interior of the sphaeroidal body, seems to have been initiated by the formation of very small (up to 10 μm) framboidal aggregates, which by growing and coalescenceing gave rise to the greater bodies that grew

until the internal cavity of each of the supposedly organic sphaeroids was completely filled. The pyritized sphaeroids from the examined sample are imperfectly spherical and show slight variation in diameter, ranging from 0.4 to 0.6 mm, 0.5 mm on average. Two of the sphaeroids show a fracture, one perpendicular to the long axis and the second in the

FOSSILS AND STRATA

tip. An isolated sphaeroid also shows a fracture in the tip. We hypothesize that these pyritized sphaeroids represent the mineralized internal moulds of invertebrate eggs, possibly even those of trilobites, especially as marine arthropod eggs seem to be quite resistant to decay (Martin et al. 2005) and can be replaced by framboidal pyrite (Hegna et al. 2017). Similar framboidal pyrite aggregates are described from hydrocarbon-bearing ecosystems where microbial organisms played an important role in their formation (Cavalazzi et al. 2012). This is common in modern seep environments (Merinero et al. 2008; Cavalazzi et al. 2012); however, the Bayo Member was deposited in a more normal geological setting on a marine platform. The lack of euhedral pyrite in the spheres points to a limited diffusion of ions between the inside and outside of the spheres. The formation of framboidal aggregates is favoured under more oxidizing conditions, while typical pyrite crystals develop under more reducing conditions (Grimes et al. 2002; Gabbott et al. 2004). This suggests that the conditions within the spheres were not too reducing or a very limited exchange with the external environment occurred. This fact agrees with the delicate pyritization process observed in the graptolites that also occur in horizon TUN-057. Their broad similarity to structures described by Hegna et al. (2017) and their direct association with complete carcasses of juvenile and adult specimens of P. (Coplacoparia) tournemini (Rouault) in the same beds, where other trilobites are mostly represented by exuviae in several degrees of disarticulation, may also suggest that this pliomerid species was the producer of the purported sphaeroidal eggs. However, the lack of a direct link with this pliomerid trilobite drives us to state that the pyritized eggs could also belong to another trilobite or another unknown arthropod. Although we agree that such an interpretation is purely hypothetical, it seems the most parsimonious one so far. The present evidence of Lower Palaeozoic arthropod eggs is very limited, being restricted to the specimens presented by Shu et al. (1999), Lin et al. (2006), Siveter et al. (2007, 2014), Duan et al. (2014), Caron & Vannier (2016) and Hegna et al. (2017). Shu et al. (1999) and Duan et al. (2014) described eggs and/or embryos associated with the bradoriid arthropod Kunmingella (Cambrian, Chengjiang Lagerst€atte). The structures are 150–180 μm in diameter and are preserved by pyrite and phosphates. In both of these cases, they are directly associated with adult specimens. Lin et al. (2006) analysed clusters of silicified sphaeroids 767 μm in mean diameter and randomly piled in layers, which are preserved in a fine-grained siliciclastic

Trilobite juveniles and possible eggs from Spain

29

matrix from the middle Cambrian Kaili Formation Lagerst€atte, south China. According to Lin et al. (2006), the eggs are primarily preserved as solid silica replacement, with the original organic layer replaced by a calcite layer covering the eggs. Siveter et al. (2007, 2014) described brood care in myodocopid ostracods from the Silurian Herefordshire Konservat-Lagerst€atte and the Ordovician Beecher’s Trilobite Bed. In the first case, the eggs and possible juveniles are about 550 μm long and are preserved in calcite that coprecipitated with pyrite and infilled the voids (see Orr et al. 2000). In the second case, the eggs and possible embryos are pyritized, ranging between 240 and 350 μm and are associated with adult individuals. Caron & Vannier (2016) described comparatively large eggs (0.7–2.4 mm) in Waptia fieldensis from the Burgess Shale. Supposed trilobite eggs have been reported by Hegna et al. (2017). These are preserved as minute pyritized bodies, elliptical in shape, and clustered below the fixigenal area of the olenid trilobite Triarthrus eatoni (Hall, 1838), from the Lorraine Group of northeastern United States. Hegna et al. (2017) interpreted these bodies as trilobite eggs by their spatial association with this particular trilobite and suggested that trilobites may have had an unmineralized ontogenetic stage before the protaspis to explain the small size of the eggs (some 200 μm in size) relative to the first protaspis larvae. In contrast to the scarcity of data relative to ancient eggs, the record of unassigned fossil embryos of problematic metazoans has been more extensively treated in the literature (Zhang & Pratt 1994; Bengtson & Zhao 1997; Steiner et al. 2004; Donoghue et al. 2006). Barrande (1852, pl. 27, figs 1–3) was the first author who reported the discovery of presumed trilobite eggs. They occur as sphaeroidal bodies of about 0.7 mm in diameter and clustered on bedding planes in number of 12 per cm2, or alternatively as isolated calcareous bodies of greater diameter (2–5 mm) preserved in trilobite-rich limestones. The first type was mentioned by Lin et al. (2006) as possible eggs, but the original sample (Barrande 1852; pl. 27, fig. 1), from the Middle Devonian Chotec Limestone of Bohemia, was reviewed by one of us (LL) and remains as unconvincing because of the preservation. The second type of sphaeroidal fossils attributed to ‘trilobite eggs’ by Barrande (1872, pl. 27 figs 2–3), derived from Ordovician rocks, are probably too large and are possibly of faecal origin. The same probably applies to the subsequently described ‘eggs of uncertain origin’ (Barrande 1872, pl. 18, figs 30– 31; pl. 35, figs 25–32, 35–36), which mostly correspond to minute ovoid pellets of Alcyonidiopsis

30

Bern
ardez et al.

[=Tomaculum] problematicum Groom, 1902 (see Eiserhardt et al. 2001; Bruthansová & Kraft 2003; Kimmig & Pratt 2008). Egg-like structures were described in thin section by Walcott (1879) but were criticized by Raymond (1920). Additional records of ‘eggs of uncertain origin’ (Hermite 1878; Bureau 1900) and even of ‘trilobite eggs’ (Marsille 1910) in the Ordovician of the Armorican Massif of western France also come from classical localities where T. problematicum is common (P
eneau 1944).

Discussion Speyer & Chatterton (1989) suggested that early post-embryonic stages of trilobites were, based on their functional morphology, either benthonic or planktonic. Chatterton & Speyer (1989) also proposed that some of the early developmental stages might have either fed on organic detritus (detritotrophic) or nourished by a large yolk (lecithotrophic) and such adaptation would increase their survivorship during the late Ordovician extinction. Recently, Laibl et al. (2017) built a database of all well-known protaspid stages from the Cambrian and demonstrated that the largest, possibly lecithotrophic, post-embryonic stages of Cambrian trilobites (ca. 0.7–1.9 mm wide) were restricted to high palaeolatitudes along the West Gondwanan margin. Some of these trilobites with large stages even have accelerated development, which is another character of recent lecithotrophic crustaceans (see Anger 2001 for detailed discussion). Interestingly, the comparatively large stages of P. mendax are morphologically and also by size comparable to the B1 stage of Brongniartella sp. described by Chatterton et al. (1990). Supposing that there were no preceding planktonic stages, these similarities might suggest a lecithotrophic feeding strategy in P. mendax as was proposed for homalonotid trilobites (Chatterton et al. 1990). Unfortunately, data about the size of the trilobite eggs are scarce. The previous supposed trilobite eggs reported from the Cambrian of South China (Lin et al. 2006) and from the Ordovician of New York (Hegna et al. 2017) are rather different from those reported herein. The Chinese specimens fall within the size range of recent arthropod eggs, and although those reported by Hegna et al. (2017) are quite small, some eggs are known of this size (Thi
ery & Gasc 1991; Shen & Huang 2008). Conversely the possible ‘eggs’ from the ‘T
unel Ordov
ıcico del Fabar’ are very large and could possibly have been produced by lecithotrophic taxa (see egg size mentioned in McEdward 1997). This is in correspondence with the large

FOSSILS AND STRATA

growth stages of P. mendax from the same locality and with the distribution of large, presumably lecithotrophic, trilobite stages in high latitudes (Laibl et al. 2017), as all the material described herein comes from northwestern Spain, located during the Middle Ordovician in high latitudes (ca. 70°S) along the margin of Gondwana. Also, the meraspid degree 2 of P. mendax is larger compared with some other meraspid degree 2 specimens (at ca. 2.2 mm in length). For instance, the total length of M2 of Hunanocephalus ovalis and Duyunaspis duyunensis from South China ranges between 0.94 and 1.39 mm and between 1.05 and 1.44 mm in length, respectively (Dai et al. 2014, 2017).

Concluding remarks Early post-embryonic stages of trilobites are very rare fossils in the Ordovician of southwestern Europe. This is in part due to the absence of suitable marine facies for the preservation of this kind of fossils as those in southern Gondwana were generally too shallow and energetic, but mainly because of the general lack of fine-grained sediments such as black shales and limestones. Herein, we describe the early post-embryonic growth stages of P. mendax, a calymenacean trilobite that was widespread in the southern margin of the Gondwana continental shelf and its Avalonian counterpart, which were both located in high palaeolatitudes during the Middle Ordovician. The smallest protaspides of P. mendax, when compared with early growth stages of other calymenid trilobites, correspond with the first benthonic stage (B1) of the protaspid period. This, when combined with the relatively large size of these protaspides and early meraspides of that species, suggests that P. mendax may have had lecithotrophic early development. Additionally, pyritized sphaeroids found in a bed rich in complete carapaces of the trilobite P. (Coplacoparia) tournemini are hypothesized to represent the remains of arthropod eggs, quite possibly those of P. tournemini because this is the only arthropod that is known to be abundant in the same bed. The size of these sphaeroids larger than previously reported for other structures that have been hypothesized to be the preserved remains of trilobite eggs (mean diameter of 0.5 mm for the Spanish material versus 0.2 mm for T. eatoni), when combined with its high latitude palaeobiogeographic location, could also be explained by lecithotrophic early development for that species. However, an alternative hypothesis suggested by Hegna et al. (2017) is that olenid trilobites such as T. eatoni may

FOSSILS AND STRATA

have had an unmineralized larval stage or stages between the egg and the first mineralized protaspid (at present undiscovered, other than a large gap in size between the structures believed to be eggs of that species and the smallest known protaspid). Thus, the size of the smallest known protaspid of a trilobite may not necessarily be used to determine the size of the eggs of that species. It is also worthy of note that some workers have suggested that olenids lived in rather unusual, for trilobites, oxygen-depleted environments at the outer edge of the continental shelf (Clarkson & Taylor 1995; Fortey 2000).

Acknowledgements We are grateful to the Spanish Ministry of Public Works (MFOM) and the company FCC Construcci
on for the facilities given to palaeontological study during the excavation of the tunnel. We also thank Carlos Alonso (Complutense University of Madrid) and Pilar Mata (Instituto Geol
ogico y Minero de Espa~ na, Madrid) for optical and SEM photography of specimens, respectively. The use of the Jeol JSM 6010LA Plus electron microscope has been partly funded by the European Regional Development Fund (ERDF) IGME13-4E-1518. The National Museum of Natural Sciences, Madrid, is acknowledged for allowing us to use the environmental SEM in this work. We are grateful for the comments and suggestions by the reviewers Brian Chatterton and Thomas Hegna that improved this work. Alan Owen and David Bruton are acknowledged for the editing of this special volume on trilobites. Our work has been supported by the Spanish Ministry of Science, Innovation and Universities, project numbers CGL2013-48877-P and CGL201787631-P. This is also a scientific contribution to the project IGCP 653 (IUGS-UNESCO). Jorge Esteve was funded by a Juan de la Cierva Grant (FPDI2013-17337). Luk
as Laibl was financially supported by Research Plan RVO 67985831 of the Institute of Geology of the Czech Academy of Sciences.

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ıa-Ramos, J.C. 1993: La sedimentaci
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FOSSILS AND STRATA Henry, J.-L. 1980: Trilobites ordoviciens du Massif Armoricain. M
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FOSSILS AND STRATA Shu, D., Vannier, J., Luo, H., Chen, L., Zhang, X. & Hu, S. 1999: Anatomy and lifestyle of Kunrningella (Arthropoda, Bradoriida) from the Chengjiang fossil Lagerst€atte (lower Cambrian; Southwest China). Lethaia 32, 279–298. Siveter, D.J., Siveter, D.J., Sutton, M.D. & Briggs, D.E.G. 2007: Brood care in a Silurian ostracod. Proceedings of the Royal Society B 274, 465–469.
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ery, A. & Gasc, C. 1991: Resting eggs of Anostraca, Notostraca and Spinicaudata (Crustacea, Branchiopoda) occurring in France: identification and taxonomical value. Hydrobiologia 212, 245–259.

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Torsvik, T.H. & Cocks, L.R.M. 2017: Earth History and Palaeogeography, 332. Cambridge University Press, Cambridge. Vanek, J. 1965: New species of the suborder Calymenina Swinnerton, 1915 (Trilobita) from the Barrandian area. Sborn
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Stratigraphy and trilobite biofacies of the Late Ordovician of the Taimyr Peninsula, Arctic Russia JAN OVE R. EBBESTAD AND RICHARD A. FORTEY Ebbestad, J. O. R. & Fortey, R. A. 2019: Stratigraphy and trilobite biofacies of the Late Ordovician of the Taimyr Peninsula, Arctic Russia. Fossils and Strata, No. 64, pp. 35–53. The Taimyr Peninsula is rich in Ordovician trilobites, some of which were described by E. A. Balashova nearly sixty years ago; these have now been supplemented by new collections. We here describe the Ordovician formations from which trilobites have been recovered in the light of much subsequent fieldwork elucidating the regional geology. Late Ordovician trilobites display two very different biofacies. Black limestone and shales such as those of the Povorotnaya Formation, a palaeoenvironment originally marginal to the Taimyr terranes, yield rich collections (termed the raphiophorid association) with many species of trilobites very like those of the peripheral Laurentian Scoto-Appalachian belt (Ampyxella, Ampxyina, Failleana, Pararemopleurides, Raymondella, Remopleurides, Robergia, Stygina, Taimyraspis, Telephina and Toernquistia). This association has been divided into two biofacies, but the small number of new collections obliges us to treat these together in the discussion in this study. From shelf limestone, a contrasting fauna has monorakine trilobites (Carinopyge, Ceratevenkaspis, Elasmaspis, Evenkaspis and Monorakos) endemic to the Siberian palaeoplate, which occur alongside trilobites such as isotelines, Xylabion and Cheirurus otherwise typical of inshore Laurentia. □ Biofacies, Late Ordovician, monorakine, raphiophorids, Scoto-Appalachian, Taimyr Peninsula, Taimyraspis. Jan Ove R. Ebbestad [[email protected]], Museum of Evolution, Uppsala University, Norbyv€ agen 16, SE 752 36 Uppsala, Sweden; Richard A. Fortey [[email protected]], Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK; manuscript received on 8/11/2017; manuscript accepted on 12/04/2018.

Introduction The Ordovician succession on the Taimyr Peninsula, Arctic Russia, is exposed in a narrow fold belt describing a 750-km-long arc across the tundra from the NE to the SW. The sedimentary succession in the fold belt is remarkably complete, spanning the Ediacaran to the Carboniferous, and the entire Ordovician is represented by some 2000 m of sediments. Platform carbonates dominate in the southern part of the outcrop area with a transition to deeper siliciclastic deposits in the northern part of the peninsula. During the last 20 years, the lithostratigraphy has been improved considerably following extensive mapping, also allowing better constraints on the biostratigraphy (Sobolevskaya & Nekhorosheva 2017). Fossiliferous strata have been studied systematically since the 1930s and several fossil groups have been monographed, including corals, stromatoporoids, crinoids, bryozoans, brachiopods, gastropods, graptolites, trilobites, ostracodes and conodonts. Nevertheless, the succession is exceedingly rich in fossils and much detailed work remains to be done, although the remoteness and

inaccessibility of the area is an enormous obstacle. Fossils are generally very well preserved, but the conodonts show a high thermal alteration (CAI 4–5; Sobolev 2003). The Taimyr Peninsula has been regarded as comprising three tectonically distinct blocks, of which the northernmost has been termed the Kara microcontinent. This region had a separate development during the Early Palaeozoic, joining in the early Silurian with Baltica and in the Late Palaeozoic with the Siberian craton (Zonenshain et al. 1990; Torsvik & Cocks 2016). Another thrust to the south of the Kara block, the Pyasino-Faddey Thrust, suggests a separation within the Ordovician sedimentary fold belt, with the northern siliciclastics separated from the southern carbonate facies. Upper Ordovician brachiopods with a Baltica affinity gave some support for this notion (Cocks & Modzalevskaya 1997; Modzalevskaya 2003), but several lines of evidence suggest instead that Taimyr is better regarded as part of the Siberian craton and lying at a passive margin (Cocks & Torsvik 2007; Nikishin et al. 2010). In general, the Middle and Late Ordovician faunas from Taimyr show a Siberian signal, with assemblages comprising widespread taxa mixed with those

DOI 10.1002/9781119564232 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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J. O. R. Ebbestad & R. A. Fortey

endemic to the Siberian craton (e.g. Melnikova 2003; Modzalevskaya 2003; Tolmacheva 2003; Khromych 2010), and the Ordovician fauna of Taimyr was early on included in a Kolymo-Siberian palaeobiogeographical province (Kanygin et al. 2010). The trilobites show a similar picture, sharing taxa with Baltica and Laurentia as well as including truly endemic Siberian genera. Trilobites were first described from Taimyr by Balashova (1959, 1960) with several other taxa being reported later in the literature but without descriptions or illustrations (but see Gogin 1997). The biogeographical affinity of the Taimyr assemblage was briefly discussed by Fortey & Cocks (2003) but an ongoing revision of the Balashova species, along with a large collection of new trilobite material (ca. 620 specimens, often with multiple specimens on each rock) collected from Taimyr in 1998, now allows a refined characterization of the Late Ordovician trilobite biofacies and biogeography of this remote region.

The Taimyr Peninsula Geography and previous research The Taimyr Peninsula is the northernmost projection of North-central Siberian Russia, comprising an area about 300 km wide (NS) and 1000 km long (EW), constituting most of the former Taimyr Autonomous Region, now part of the larger Krasnoyarsk Krai administrative region. It is bounded by the estuary of the Yenisei River and the southern Kara Sea in the west, the Laptev Sea in the east, the Khatanga River in the south; Cape Chelyuskin at the tip of the peninsula is the northernmost point of the Eurasian landmass. The peninsula is mostly tundra drained by the Upper and Lower Taimyr rivers, running into the centrally sited Taimyr Lake and flowing northwards to the Kara Sea. Geographically, it is divided into western Taimyr extending from the Yenisei Gulf to the Pyasina River, central Taimyr extending from the Pyasina River to the Lower Taimyr River, and eastern Taimyr extending from the right bank of the Lower Taimyr River to the coast of the Laptev Sea (Fig. 1A). Right and left banks are named relative to the view downstream. Previous research on the Ordovician of the Taimyr Peninsula is extensive, and a few key papers are listed here. The expedition of Urvantsev in 1929 (Urvantsev 1931) was the first study of the Ordovician in the Taimyr Peninsula; information from such early expeditions was summarized by Bondarev & Cherkesova (1967) and Bondarev et al. (1968). Important studies during this period included the first stratigraphical

FOSSILS AND STRATA

framework by Zlobin (1956, 1958) and several taxonomic works particularly those of Balashova (1959, 1960) on the trilobites collected by Zlobin in the early 1950s. Bondarev et al. (1968) updated and modified the stratigraphical framework, including stratotypes and fossil distributions (see also summary in Bondarev 1968). Some years later, an updated Ordovician stratigraphy was presented (Nekhorosheva et al. 1983, 1988; Bezzubtsev et al. 1986) giving better age constraints on some units. The modern understanding of the Ordovician of the Taimyr Peninsula stems from a series of papers on the stratigraphy and faunas, including widespread graptolites (Sobolevskaya 1988, 2003, 2011; Sobolevskaya et al. 1995, 1997, 1999, 2000; Koren et al. 2006; Bagaeva & Zastrozhnov 2013; Sennikov et al. 2015; Sobolevskaya & Nekhorosheva 2017), coupled with development of new geological maps (Gromov et al. 2015; Onischenko et al. 2000a, b, 2001a, b; Paderin & Schneider 2011a, b; Paderin et al. 1997; Proskurnin et al. 2015; Schneider et al. 2001, 2013; Sobolevskaya et al. 2009; references only to map sheets showing Ordovician strata). These works allow us to assess the distribution of the trilobite facies and occurrences given by Balashova (1959, 1960) in relation to current understanding of the stratigraphy of the Taimyr Peninsula and modern Ordovician stratigraphical terminology (Bergstr€om et al. 2009). What is currently lacking regarding the Taimyr succession are studies on chemostratigraphy. Further information on conodonts is also needed (but see Tolmacheva 2003; Sennikov et al. 2015). The map in Figure 1 shows the geographical position and terminology of the peninsula (Fig. 1A), the geology of the study area discussed herein (Fig. 1B) and the general structural areas and facies belts (Fig. 1C).

Structural setting The geological structures of the Taimyr Peninsula describe a wide NE–SW arch. The northernmost part has been recognized as the separate Kara block (Zonenshain et al. 1990), while to the south of the Main Taimyr Thrust, Ediacaran to Carboniferous sedimentary cover rocks overlie the older basement (Fig. 1C). These were folded during the collision between the Kara block and northern Siberia in the Late Palaeozoic – Early Triassic (Vernikovsky 1996, 1997; Metelkin et al. 2005; Zhang et al. 2013) or later in the Mesozoic (Zonenshain et al. 1990; Torsvik & Andersen 2002; Zastrozhnov et al. 2014). Traditionally, the peninsula has been divided into the northern (Kara) domain, as well as a central and a southern domain. The latter domain should be joined along the Pyasino-Faddey Thrust (Zonenshain et al. 1990;

Trilobite biofacies, Late Ordovician of Taimyr

Fig. 1. Geographical, geological and structural maps of the Taimyr Peninsula. Based on references given in the text for each formation. A, the Taimyr Peninsula with main rivers and geographical names and areas. B, geological map of eastern Taimyr, showing Ordovician and undifferentiated Silurian sediments in the fold belt, stratigraphical regions and areas, and key localities. C, major structural elements of the Taimyr Peninsula, with stratigraphical regions indicated.

FOSSILS AND STRATA 37

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J. O. R. Ebbestad & R. A. Fortey

Vernikovsky 1996, 1997), but Inger et al. (1999) found no evidence for such a thrust within the central and southern domain, which, if present, must be buried underneath the sedimentary cover (Torsvik & Andersen 2002). For the purposes of this paper, a suture line within the central and southern domain is omitted from the structural map (Fig. 1C) to highlight the continuity of the Ediacaran to Carboniferous sedimentation. The northern part is the Kara block, in a tectonic sense, while the area to the south is referred to as south-central Taimyr in a geographical sense.

Facies regions and areas Ordovician sediments on the Taimyr Peninsula can be traced as narrow discontinuous outcrops for a distance of 750 km from the Pyasina Gulf in the west to the Laptev Sea in the east, an outcrop area that is 15– 50 km wide (Bondarev et al. 1968). When exposed within the fold belt, the Ordovician generally forms the limbs of synclines and the cores of larger anticlines (Nekhorosheva et al. 1988). Zlobin (1956, 1958) recognized that the rocks to the north differed from those in the south, the former being dominated by deeper water terrigenous sediments and the latter being dominantly platform carbonates. Subsequently, these two areas were referred to as the Northern Structural Facies Zone and the Southern Structural Facies Zone and separate stratigraphical schemes were developed in the two areas (Obut & Sobolevskaya 1964; Bondarev & Cherkesova 1967; Bondarev et al. 1968; Nekhorosheva et al. 1988; Sobolevskaya et al. 1999; Sobolevskaya & Nekhorosheva 2017), although a transitional zone with mixed sedimentation was also recognized (Sobolevskaya et al. 1995, 1999; Tesakov et al. 1995). Following the new 1:200,000 and 1:1,000,000 scale, geological maps developed for the area (Gromov et al. 2015; Onischenko et al. 2000a, b, 2001a, b; Paderin & Schneider 2011a, b; Paderin et al. 1997; Proskurnin et al. 2015; Schneider et al. 2001, 2013; Sobolevskaya et al. 2009; map sheets showing Ordovician strata only), the structural facies zones for the Ordovician, Silurian, and Devonian deposits were divided into new stratigraphical regions and areas (Sobolevskaya 2003, 2011). The northernmost region was termed the Pyasina-Leningrad Stratigraphical Region (1), the central zone the LenivayaKlyuevka Stratigraphical Region (2) and the southernmost the Tareya-Faddey Stratigraphical Region (3). Each region was further divided into eastern and western areas, corresponding to the Pyasina (1a) and Gol’tsov (1b) stratigraphical areas for zone 1, the Rogatin (2a) and Lower Taimyr (2b)

FOSSILS AND STRATA

stratigraphical areas for zone 2, and the Tareya (3a) and the Nyun-karaku Tari (3b) stratigraphical areas for zone 3 (Fig. 2). The northern region (region 1) corresponds to the more siliciclastic deposits, region 2 to the transitional facies and region 3 to the carbonate-dominated facies. The position of the regions shifted slightly through time (Onischenko et al. 2000a, b; Sobolevskaya 2003). Subsequently, new region names were adopted and the former area names dropped except for the southern carbonate facies. The new regions include the area of the Kara block: Region I – KhutudabigayChelyuskin (Kara block), Region II – Lenivaya-Shirokaya (deeper facies), Region III – Tareya-Pregradnaya (transitional facies), Region IV – TareyaFaddey (carbonate facies) (Fig. 2) (Sobolevskaya 2011; Sobolevskaya & Nekhorosheva 2017). However, in this study, the former regional divisions are also presented (Figs 1, 2), because they correspond to the modern published geological maps. Approximate boundaries of regions and areas are shown in Figures 1A, C, and 2 (‘stratigraphical’ is omitted for simplicity).

Stratigraphy Units, ages and fossils The Ordovician of the Taimyr Peninsula is presently divided into ‘horizons’ (~stages in non-Russian terminology) and formations (‘suits’ in Russian terminology) but Sobolevskaya (2011) refrained from using the ‘horizons’ because of problems with boundary definitions and lack of updated taxonomy of several fossil groups used to define the original horizons (Bondarev et al. 1968). Formations encompass regional units but give their names also to horizons (~stages). So the Toll Formation (Darriwilian) is a subdivision of the Toll Horizon, which spans the Floian to the Darriwilian (Koren et al. 2006; Sennikov et al. 2015). The northern graptolitic facies were often subdivided into local graptolite zones (Nekhorosheva et al. 1988) before the revision by Sobolevskaya (2011). The units relevant to this study are briefly outlined below in stratigraphical order, starting with the oldest and arranged from west to east. For each unit, the transliterated Russian name is given in parentheses, using the ISO 9:1995 standard (this is also used for Russian journals and books in the reference list). Stratotype or reference sections are encircled in Figure 1B, with a corresponding number in the text and figure. Three key sections have been studied by Ebbestad which allow a clear

FOSSILS AND STRATA

Trilobite biofacies, Late Ordovician of Taimyr

39

Fig. 2. Stratigraphy of the Ordovician succession on the Taimyr Peninsula. A, development of the stratigraphical subdivisions. B, modern stratigraphical subdivisions within the three stratigraphical regions and correlation with global and Siberian Ordovician stages. The upper region names in the head row, denoted with roman numerals, are those given by Sobolevskaya & Nekhorosheva (2017), while the lower region names are those given in Sobolevskaya (2003) and used in the hitherto published modern geological maps (see text for references). Black stars indicate a monorakine-cheirurid-illaenid association while the black squares indicate the raphiophorid association. Hi, Hirnatian; Ka, Katian; Sa, Sandbian; Dar, Darriwilian; Bur., Burian; Nir., Nirundian; Bak., Baksian; Che., Chertovskian; Kir.-Kudr., KirenskoKudrinian; Volg., Volginian. Modified from Sobolevskaya (2003) and Sobolevskaya & Nekhorosheva (2017). Zonation and stages are based on Bergstr€om et al. (2009) and Sennikov et al. (2015).

delimitation of trilobite biofacies. Occurrences of trilobites for each unit are given while some of the other important fossil groups are also indicated. Global stages and subdivisions follow Bergstr€om et al. (2009) while the Siberian stages and

correlations are based on Sennikov et al. (2015) and Kanygin et al. (2017). More detailed descriptions of each unit are found in Bondarev et al. (1968), Nekhorosheva et al. (1988); Onischenko et al. (2000a, b), Schneider et al.

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J. O. R. Ebbestad & R. A. Fortey

FOSSILS AND STRATA

(2001), Sobolevskaya et al. (2009), Proskurnin et al. (2015) and Sobolevskaya & Nekhorosheva (2017), but a summary is useful here as some of these publications are difficult to obtain.

Table 1. Stratigraphical distribution of trilobite species described by Balashova (1959, 1960). Taxa in Balashova (1959, 1960)

Current placement

Units in Balashova (1959, 1960)

Vesenn’aya Formation (Vesenninska^a tol^sa)

Ampyx spp. (2) Ampyxina taimyrica Balashova Bronteopsis scoticus Etheridge & Nicholson Bumastus holei Foerste var. taimyrica Balashova Caphyra spp. (2) Ceraurinus sp. (3) Goldillaenus taimyricus Balashova Homotelus spp. (2) Isoteloides spp. (2) Isotelus spp. (3) Monorakines (3) Robergia barrandei Etheridge & Nicholson Sphaerexoxhus taimyricus Balashova Stygina latifrons Salter Taimyraspis taimyrica Balashova Tetralichas taimyricus Balashova Stenopareia spp. (2)

Povorotnaya Povorotnaya

Povorotnaya Toll

Povorotnaya

Toll

Povorotnaya

Povorotnaya

Povorotnaya Povorotnaya Povorotnaya

Povorotnaya Povorotnaya Povorotnaya

Povorotnaya Povorotnaya Povorotnaya Povorotnaya Povorotnaya

Povorotnaya Povorotnaya Povorotnaya Povorotnaya Toll

Povorotnaya

Povorotnaya

Povorotnaya Povorotnaya

Povorotnaya Toll

Povorotnaya

Povorotnaya

Tolmachev, Povorotnaya Tolmachev

Tolmachev, Povorotnaya Tolmachev

Tolmachev

Tolmachev

Tolmachev Tolmachev Tolmachev Engelgardt, Tolmachev Engelgardt Engelgardt Engelgardt Toll, Engelgardt

Tolmachev Tolmachev Tolmachev Druzhnov, Tolmachev Druzhnov Druzhnov Druzhnov Toll, Druzhnov

Toll Toll

Toll Toll

Stratotype. – The formation was established by Sobolevskaya in Khapilin et al. (1986) on the upper parts of the Vesenn’aya River (left tributary to the Trautfetter River (no. 1 in Fig. 1B)). Originally, it was named the Ostantantsovaya Formation (Ostancovska^a Svita) but was later renamed. It is well developed in the stratotype area, which is just north and northwest of the Vesenn’aya River (around the Ustremlennaya River area near no. 5b in Fig. 1B). (Schneider et al. 2001; Sobolevskaya 2011). Remarks. – The formation is composed of siltstones with thin carbonate beds, some showing cross-bedding, and large silty carbonate concretions. Exposures are limited but the thickness is estimated to be up to 450 m. It is part of the transitional Lower Taimyr Area (2b). The age spans the Floian to Sandbian based on graptolites (Sobolevskaya 2011). Both Bronteopsis and Ampyx have been reported from this unit (Bondarev et al. 1961) but their occurrence has not been confirmed in modern times. Sobolevskaya (2011) reported rare Dionide sp. in a section just south of the Middendorf Cave. Melnikova (2002, 2003) described a mixed ostracod assemblage from this unit, containing elements that may indicate deep water facies.

Toll Formation (Tollevska^a Svita) Stratotype. – The unit was separated as the lowest part of the Middle Ordovician by Zlobin (1956), who distinguished a stratotype section near the mouth of the Toll River, a left tributary of the Klyuevka River (no. 2 in Fig. 1B). Remarks. – Most of the Toll Formation comprises dark grey to black limestone intercalated with thin calcareous mudstones that become more dominant higher in the unit. The formation may be up to 600 m thick and is part of the carbonate-dominated areas in region 3. It is exposed in the eastern areas as well as in a synform at the northern part of Lake Engelgardt (see Fig. 1B) from where Zlobin (1956) reported finds of Bronteopsis and Ampyx in the lower parts of the formation (but see Biofacies discussion). Asaphids were mentioned in the upper parts (Onischenko et al. 2000a, b). In addition to graptolites, Balashova (1959, 1960) referred to nine trilobite taxa from the Toll Formation

Ampyx depressus (Angelin) var. otradnica Balashova Bronteopsis nannus Balashova Ceraurinus sp. (5) Illaenus spp. (2) Monorakines (8) Lonchodomas rostratus var. taimyrica Balashova Illaenus spp. (2) Remopleurides spp. (2) Vogdesia nordica Balashova Basilicus tyrannus (Murchison) Illaenus/Stenopareia spp. (3) Raymondella nordica Balashova

Species are arranged in stratigraphical order and alphabetically within each unit. The number in parentheses behind each taxon indicates number of species. The stratigraphical position given by Balashova is presented in the last column.

(Table 1) while Bondarev et al. (1968) listed Cybele, Robergia, Remopleurides and Triarthrus from the upper part of the Toll Formation.

 Engelgardt Formation (Engel’gardtovska^ a Svita) Stratotype. – The unit was first mentioned by Bondarev & Cherkesova (1967) but defined by Bondarev et al. (1968). It is equivalent to the Druzhnaya Formation of Zlobin (1956), which was studied in the Pregradnaya River area but never used as a name.

FOSSILS AND STRATA

The stratotype section is at the upper part of the Galechnaya River, along the left tributary named the ‘Ordovician Stream’ (Sobolevskaya 2003) east of the Engelgardt Lake (no. 3 in Fig. 1B). Remarks. – The unit is dominated by organic-rich limestone, with subordinate mudstone, and is quite fossiliferous. Its lower boundary is marked by a limestone horizon containing nodules of chert. The formation may be up to 600 m thick and is part of the carbonate-dominated areas in region 3. Graptolites place the unit within the Hustedograptus teretiusculus Zone (Koren et al. 2006; Sennikov et al. 2015) (Fig. 2B), and ostracods from the Engelgardt Formation are known from the Darriwilian of the Siberian Platform (Melnikova 2003). The most complete succession of the Engelgardt Formation is on the right bank of the Lower Taimyr River just 4 km north of the outlet of the Tolmachev River (Onischenko et al. 2000b; Sobolevskaya 2003) (no. 4 in Fig. 1B). From here Lonchodomas, Illaenus and Calliops were reported in the lower part, with Lonchodomas, Ampyx, Isotelus, Ceraurinus, Remopleurides and Calliops occurring higher in the section (Onischenko et al. 2000b). Sobolevskaya et al. (2009) and Proskurnin et al. (2015) reported Ampyx and Calyptaulax from this unit, while Eorobergia and Lichas have been mentioned from other sites (Onischenko et al. 2000a, b).

Tolmachev Formation (Tolmacevska^a Svita) Stratotype. – The stratotype of the Tolmachev Formation follows directly on the Engelgardt Formation at the section mentioned earlier; the right bank of the Lower Taimyr River, about 4 km from the mouth of the Tolmachev River (no. 4 in Fig. 1B). The unit and stratotype were distinguished by Zlobin (1956) and further defined by Bondarev et al. (1968). Remarks. – The base of the formation is marked by a sequence of mottled dark red and green mudstones that can be recognized over a large area. The middle of the formation is dominated by limestone, while the upper is again predominantly mudstones (Onischenko et al. 2000b). The formation may be up to 600 m thick and is part of the carbonate-dominated areas in region 3. Bryozoans, brachiopods, ostracods and conodonts show clear affinity with species in the Ordovician of the Siberian platform, indicating a Chertovskian to Baksian age (=Sandbian 1) (Melnikova 2003; Modzalevskaya 2003; Sobolevskaya 2003; Tolmacheva 2003). Balashova reported 20 species of trilobites from the Tolmachev Formation, including mostly

Trilobite biofacies, Late Ordovician of Taimyr

41

monorakines, isotelines, cheirurids and illaenids (Table 1). Bondarev et al. (1968) reported Isotelus and Isaulax in the lower part of the unit (see also Schneider et al. 2001). Specimens of Xylabion and a monorakine were collected from the lower beds of the type section by Ebbestad, while Onischenko et al. (2000b) reported Isotelus in the lower part, and Monorakos and Ceraurinus in the middle to upper parts of the type section (see also Schneider et al. 2001). Paderin et al. (1997) also found Monorakos high up in the unit at the Solnechny rivulet (not shown on map in Fig. 1B). In a measured section near the mouth of the Toll River (near no. 1 in Fig. 1B), Sobolevskaya (2003, fig. 8) registered Bumastus, Illaenus, Stenopareia, Ampyx, Homotelus, Ceraurinus and Calliops (distribution repeated in Proskurnin et al. 2015), along with numerous taxa of ostracodes and bryozoans. However, two of the trilobite species, I. valvulus and H. taimyricus, are Balashova species that originally were found in the Toll and Povorotnaya formations respectively.

Barkov Formation (Barkovska^a Svita) Stratotype. – The unit was named by Zlobin (1956) from the Barkov River but a stratotype was not given, the formation boundaries were unclear, and the original concept was much wider than today (Sobolevskaya et al. 2000, 2009). Subsequently, Sobolevskaya et al. (2000) selected three localities and made a composite section: (a) the east bank of the Lower Taimyr River ca. 8 km south of the mouth of the Trautfetter River (no. 5a in Fig. 1B), (b) at the Ostantsovaya River (left tributary to the Trautfetter River) ca. 18 km from its mouth (No. 5b in Fig. 1B) and (c) the Leningradskaya River ~40 km east of the mouth of the Barkov river (no. 5c in Fig. 1B). Remarks. – Most of the Barkov Formation consists of dark organic-rich mudstone with intercalated beds of siliceous limestone. The mudstone contains graptolites, while unsorted shell accumulations are found on bedding planes in the limestone. The unit is ca. 250–400 m thick, and part of the transitional Lower Taimyr area (2b). Beds of the uppermost Ordovician Barkov Formation are most complete along tributaries to the Trautfetter River, yielding graptolites of the supernus and persculptus biozones (Sobolevskaya et al. 1995). A section just north of the Middendorf Cave has yielded a rich fauna of graptolites including Orthograptus quadrimucronatus and Dicellograptus complanatus (see Onischenko et al. 2000a, b). Abundant trilobite specimens were collected by Ebbestad from the same site, including Ampyxoides, Robergia

42

J. O. R. Ebbestad & R. A. Fortey

FOSSILS AND STRATA

and Dionide (no. 6 in Fig. 1B. See Fig. 4 for the distribution of genera at this locality). A section along the Pryamaya River, a left tributary to the Lower Taimyr River (no. 7 in Fig. 1B), yielded brachiopods comparable to Upper Ordovician brachiopods from the Boda Limestone in Sweden (Cocks & Modzalevskaya 1997; Modzalevskaya 2003). Originally, this section was mapped as the Korotkaya Formation, an equivalent to the Povorotnaya Formation and part of the southern facies zone, but Sobolevskaya (2003) included it in the Barkov Formation and part of the transitional region. Exposures of the contact with the lower Silurian Dvoinaya Formation are few (i.e. at the Taimyr River north of the Middendorf Cave and Bunge River), but although sedimentation here appears to have been continuous, graptolites of the vesiculosus-cyphus Biozone indicate that the lower Rhuddanian may be missing (Sobolevskaya et al. 1995; Tesakov et al. 1995; their outcrop 90–216). Whether part of the Hirnantian is missing is unclear. Odontopleurids, proetids, lichids, illaenids and Bumastus have been mentioned from the lower part of the Ostantsovaya section and other sites (Onischenko et al. 2000a, b; Schneider et al. 2001; Proskurnin et al. 2015).

(Onischenko et al. 2001b). Conodonts were extracted from the samples in the lower part containing Taimyraspis and kindly investigated by Dr T. Tolmacheva (at that time at the Palaeobiology department at Uppsala University). The section at the Fisherman’s Bend was sampled at three different levels: the lower 30–40 m of the section with mudstone containing among others Taimyraspis, a massive limestone unit at 63–70 m with Ampyxella and Stygina, and a shale with interbedded limestone at 90–140 m with Ampyxella, Failleana and Raymondella. See Figure 4 for the complete distribution of genera at the various levels. Although the conodont fauna is generally cosmopolitan, its composition is similar to that described by Tolmacheva in Sennikov et al. (2015, p. 603; the youngest assemblage) from the Mutnyj Formation (see also Sobolevskaya 2003; Tolmacheva 2003); the assemblage was correlated by these authors with the Dolborian Stage of the Siberian platform (Katian). Paderin et al. (1997) reported Ceraurinus, Stenopareia, Isotelus and Evenkaspis in the upper parts of the formation. Bondarev et al. (1968) reported Bumastus, Illaenus, Elasmaspis, Proetus and Ceratevenkaspis in the lower part of the Korotkaya Formation (middle to upper part of the Povorotnaya Formation).

Mutnyj Formation (Mutninska^a svita)

Povorotnaya Formation (Povorotninska^a svita)

Stratotype. – The formation was named by Bezzubtsev et al. (1986) from the Mutnyj rivulet, a right tributary to the Tareya River in Central Taimyr with the stratotype near the mouth of the river (east of the map area in Fig. 1B). Remarks. – The lower boundary of this formation is marked by thick limestone beds containing nodules of black chert (Paderin et al. 1997). In its distribution, faunal content and sedimentology, the Mutnyj Formation corresponds to the now discontinued Taimyr and Korotkaya formations. The Mutnyj Formation seems to be quite similar to the Povorotnaya Formation in the Nyun-karaku Tari Area (3b), and they may eventually be considered synonymous (Proskurnin et al. 2015). The formation is 400– 500 m thick and is part of the carbonate-dominated areas in region 3. The Fisherman’s Bend is a locality on the right bank of the Taimyr River a few kilometres north of Lake Engelgardt that was collected by Ebbestad (no. 8 in Fig. 1B. See also Inger et al. 1999) and abundant specimens of Taimyraspis were found (Fortey & Ebbestad 2017). The outcrop was assumed to belong to the Mutnyj Formation, although the strata are now mapped as the Povorotnaya Formation

Stratotype. – The formation was named by Zlobin (1956) with the stratotype being at the Povorotnaya River, a right tributary to the Nyun-karaku Tari River (no. 9 in Fig. 1B). Remarks. – As with the Mutnyj Formation, the lower boundary is marked by limestone with abundant cherts, but chert also occurs in the upper part of the unit (Onischenko et al. 2000a, b). The formation is 400–650 m thick and is part of the carbonatedominated areas in region 3. Onischenko et al. (2000b) studied a section on the left bank of the Lower Taimyr River, nearly opposite the Fisherman’s Bend locality (no. 8 in Fig. 1B) and attributed this to the upper part of the Povorotnaya Formation. The Fisherman’s Bend locality exposes a slightly lower position in the formation, which is confirmed by the conodonts (discussed under the Mutnyj Formation above). While Onischenko et al. (2000b) did not report trilobites, the Fisherman’s Bend locality has yielded a diverse assemblage (see section on Biofacies). In a measured section on the right bank of the Lower Taimyr River, near the stratotype of the Tolmachev Formation (no. 4 in Fig. 1B), Stenopareia,

FOSSILS AND STRATA

Bumastus and Tetralichas have been reported (Onischenko et al. 2000b; Schneider et al. 2001).

Trilobite distribution and biofacies Stratigraphical distribution Balashova (1959, 1960) described 53 species of trilobites from the Ordovician of the Taimyr Peninsula, based on material collected mostly by the geologist M.N. Zlobin in the early 1950s. Zlobin collected in the eastern Taimyr, from about 20 unique localities, but the sample numbers and localities are, with a few exceptions, difficult to relate to the present-day geology. However, it seems clear that all species come from the carbonate-dominated facies of the PyasinaLeningrad Region (region 3) and the Nyun-karaku Tari Area (3b). Newer literature can confirm some of the occurrences, while specimens collected by Ebbestad make it necessary to revaluate some occurrences. Table 1 shows the current consensus of the distribution of the Ordovician taxa described by Balashova (1959, 1960). Note that no attempts have been made to adjust species names at this point as a revision is currently being undertaken by the authors. Figure 3 shows a representative selection of trilobite taxa from the Late Ordovician of the Taimyr Peninsula, and Figure 4 shows the distribution of trilobites in the three sections collected by Ebbestad. One of the characteristic species in the Ordovician of Taimyr, Taimyraspis taimyrica, was described by Balashova (1959, 1960) from the Toll Formation, but this position is considered erroneous. Sampling by Ebbestad at the Fisherman’s Bend locality in 1998 showed that Taimyraspis is very abundant and cooccurs with Ampyxina taimyrica Balashova there, as well as with Bronteopsis (B. scoticus sensu Balashova) and Robergia. Lithology and conodonts place these firmly within the Povorotnaya Formation (see above for discussion of the Mutnyj and Povorotnaya formations). Balashova’s material of Taimyraspis shares sample numbers with her Bronteopsis and Ampyxina specimens (i.e. sample no. 357, Lower Taimyr River and no. 249 upper part of the Klyuevka River), while the Robergia material has a sample number close to one of the Bronteopsis specimens (i.e. sample no. 1234e, Bolshaya Osevaya River, left bank, and 1234c, Bolshaya Osevaya River, left side of the valley 13 km above the mouth, respectively); no other taxa share these sample numbers (data from Balashova 1960). This supports the association we find at the Fisherman’s Bend locality and therefore the Balashova species are probably considerably younger than previously assumed. Bronteopsis has been mentioned

Trilobite biofacies, Late Ordovician of Taimyr

43

from the Vesenn’aya Formation (Bondarev et al. 1961), but this is unconfirmed. The stratigraphical position of other species from the Toll Formation remains unchanged. Trilobites endemic to Siberia are limited to the monorakines, while Taimyraspis can now be related to similar forms outside Siberia, especially Laurentia (Fortey & Ebbestad 2017). Other fauna, such as brachiopods, bryozoans, stromatoporoids, ostracodes and conodonts, show for the most part a distinct Siberian connection (see for instance Sobolevskaya 2003). Taxa within the Monorakinae, such as Carinopyge, Ceratevenkaspis, Evenkaspis and Monorakos, already occur in the Engelgardt Formation although the highest abundance is within the Tolmachev Formation (stars in Fig. 2B). In the Povorotnaya Formation, monorakines are known from the higher parts (star in Fig. 2B). Typically, the monorakines occur with Ceraurinus, Isotelus, illaenids and Calliops/Calyptaulax (see also Holloway 2004).

Biofacies The distribution of trilobites in the Ordovician of the Taimyr Peninsula is considered partly from the literature and partly from the sampling done in 1998 at three sections along the Lower Taimyr river: (1) near the Engelgardt Lake, (2) at the Fisherman’s Bend and (3) at the Middendorf Cave (Fig. 4; see also Fig. 1 for locations). These sections form the basis for the biofacies associations discussed herein. Although there are relatively few collections involved and the presence/absence data (Figs 4, 5A) show a clear distinction between the assemblages found at these, a cluster analysis focusing both on the samples (Rmode) and the variables (Q-mode) was performed to aid visualization of our assemblage distribution. Both the Dice and the Jaccard similarity indexes were tested, using the paired group algorithm (Hammer & Harper 2006) yielding only differences in branch lengths. The calculations were made using Microsoft Excel© and PAST 3.19 (Hammer et al. 2001). Both the Fisherman’s Bend and the Middendorf Cave sections were well sampled in the field, whereas at the Engelgardt locality, only a single bed was sampled. For the latter, data from the literature (see discussion of the Tolmachev Formation) were therefore added to the presence/absence matrix. Consequently, the Engelgardt samples were also omitted for the sample diversity estimates, while the diversity of the collections from the Fisherman’s Bend and Middendorf Cave localities was tested using individual rarefaction in PAST. Figure 5B shows that the pooled data from the

44

J. O. R. Ebbestad & R. A. Fortey

Fisherman’s Bend locality (mean ca. 22) and a breakdown of the same section into the three levels corresponding to different facies. The lowest level (30–40 m), with Taimyraspis, appears well sampled,

FOSSILS AND STRATA

whereas both the 63–70 and 90–140 m intervals are under sampled; a one-sample t-test shows the taxon count of these two to be significantly different from the lowest level.

FOSSILS AND STRATA

Trilobite biofacies, Late Ordovician of Taimyr

45

Fig. 3. Representative trilobite taxa of the Late Ordovician biofacies of the Taimyr Peninsula, Arctic Russia. PMU = Palaeontological collections, Museum of Evolution, Uppsala University, Sweden; CNIGRM = Central Scientific-Research Geological Exploration Museum, St. Petersburg, Russia. A–I, members of the raphiophorid association. J–N, members of the monorakine-cheirurid-illaenid association. A, Cranidium of Taimyraspis taimyrica Balashova, 1959, Povorotnaya Formation (PMU 30281/2). B, Cranidium of Robergia sp. 1, Povorotnaya Formation (PMU 30287/2). C, Cranidium of Bronteopsis sp., Povorotnaya Formation (PMU 30100/5). D, Cranidium of Ampyxina taimyrica Balashova, 1959, Povorotnaya Formation (PMU 30225). E, Cranidium of Failleana sp., Povorotnaya Formation (PMU 30135b). F, Cranidium of Ampyxella borealica (Balashova, 1959), Povorotnaya Formation (PMU 30195). G, partially articulated specimen of Raymondella sp., Povorotnaya Formation (PMU 30200). H, Cranidium of Robergia sp. 2, Barkova Formation (PMU 30326/10). I, Cranidium of Dionide sp., Barkov Formation (PMU 30303/4). J, Cranidium of Evenkaspis (Evenkaspis) nordica (Balashova, 1959), Tolmachev Formation (CNIGRM 89/8153). K, Cranidium of Calliops taimyricus Balashova, 1959, Povorotnaya Formation (CNIGRM 83/8153). L, Complete specimen of Stenopareia borealicus Balashova, 1959, Povorotnaya Formation (CNIGRM 63/8153). M, Cephalon and anterior thoracic segments of Ceraurinus nordicus Balashova, 1959, Tolmachev Formation (CNIGRM 107/8153). N, Cranidium of Carinopyge? spinifera Balashova, 1959, Tolmachev Formation (CNIGRM 104/8153). Scale bars for A, B, D, G–I = 0.1 cm, for C, E, F, J–N scale bars = 0.5 cm.

Fig. 4. Abundance measurements for localities investigated in this study. A–E, Species abundance in three sections along the Lower Taimyr River. F, inset map showing position of localities with corresponding numbers. See also Fig. 1 for position of the area shown in E. A– C, distribution of species and number of specimens in the Fisherman’s Bend section (locality 2), going from (C) the stratigraphically oldest layers of mudstone, through (B) massive limestone with chert nodules and finally (A) shale with limestone horizons. D, the material from the Engelgardt section (locality 1) was found in a 1-m-thick massive sandstone layer. See text for other species found in the Tolmachev Formation at this locality. E, specimens from the Middendorf Cave section (locality 3) come from limestone beds in black graptolitic shales.

The trilobite faunas of Taimyr are developed in at least two distinct biofacies. Relatively shallow water limestones yield a monorakine-cheirurid-illaenid association, which is likely to represent the typical biofacies of the inner shelf Siberian platform. By

contrast, dark limestones and shales occupy the greater part of the succession and yield a richer range of genera, here termed informally the raphiophorid association after its commonest component (Fig. 3). The Q-mode analysis (Fig. 5A) separates the

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Fig. 5. Quantitative visualization of association distributions in the Late Ordovician of the Taimyr Peninsula. A, cluster analysis (paired group algorithm and the Dice similarity index). The Q-mode separates three clusters which corresponds directly to the faunas in each level, demonstrating the negligible mixing of the faunas. Taxa in bold are the most common in each association. B, comparison of taxon counts in the different collections. The calculations were made using Microsoft Excel© and PAST 3.19 (Hammer et al. 2001).

lower 30–40 m in the Fisherman’s Bend section from the two upper levels, which further suggests that the raphiophorid association can be divided into two biofacies. The upper association, with Failleana and Raymondella, although under sampled, shows a low diversity fauna that is comparable to the Nahannia-Failleana biofacies of Carlucci & Westrop (2015) recognized from Oklahoma. As with the fauna in the lower part of the section, the taxa recorded higher up are both geographically widespread and have a long temporal range. For convenience, they are included within the raphiophorid association sensu lato. The monorakine-cheirurid-illaenid association comprises disarticulated fragments of thick-shelled species with trilobites belonging to the Order Phacopida dominant. Siberian endemics are confined to this biofacies, as discussed further below. There is very little, if any, mixing between the two monorakine and raphiophorid faunas (Figs 4, 5), which may suggest that the introduction of the raphiophorid association into the succession might have

been related to relatively rapid sea level fluctuations and/or climatic perturbations. There is no reason to doubt that the raphiophorid and remopleuridid trilobites were living where they are preserved as fossils. In the first place, there is common articulated material, some of which may represent moulting configurations. For example, several of the raphiophorids are preserved as axial shields, lacking cephalic doublure and genal spines. Second, other species show good ontogenetic series, such as Dionide and Taimyraspis, with sclerites ranging from a millimetre or two to adult proportions. They must have spent much of their life cycles in the same habitat. Protaspides have not been found; possibly this dispersive phase was part of the plankton, and the better fossil record followed upon settlement. Raphiophorids lacked eyes, but other elements in the fauna (Failleana, Bronteopsis, Robergia) had normal eyes, so there is no reason to suspect that these trilobites lived below the photic zone, although the articulated moults do indicate a habitat well below storm wave base. Nor is there much evidence of

FOSSILS AND STRATA

Trilobite biofacies, Late Ordovician of Taimyr

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Fig. 6. Palaeogeographical reconstruction of the Ordovician world in the Katian (450 Ma), with the distribution of the monorakine-cheirurid-illaenid (white stars) and the Scoto-Appalachian faunas (white squares). NSI, New Siberian Islands. Map from Global Paleogeography and Tectonics in Deep Time ©2016 Colorado Plateau Geosystems Inc., used under an Academic Content License Agreement.

deoxygenation in the Povorotnaya Formation, as olenid trilobites such as Triarthrus and other specialists for dysaerobic environments have not been recovered. Graptolites indicate free connection with the open ocean, and a few pelagic trilobites of the genus Telephina are consistent with this. The seafloor was soft and muddy enough to support large numbers of raphiophorids, which may have lived as filter feeders (Fortey & Owens 1999; Fortey 2014). Taimyraspis probably had similar habits judging from new information on its morphology. On the other hand, aulacopleuroid trilobites having natant hypostomes are rare, so particle feeding trilobites were not favoured. Robergia, Bronteopsis and Failleana include larger species with conterminant hypostomes that probably included scavenger/predator modes of life. The Monorakinae is a subfamily within the Pterygometopidae (Holloway 2004) and each of its four subfamiles shows distinct biogeographical distributions (Ludvigsen & Chatterton 1982; Adrain 2013). The subfamily Monorakinae is quite species-rich, with more than 40 species of Carinopyge, Ceratevenkaspis, Elasmaspis, Evenkaspis and Monorakos. Generally, they occur with the otherwise typical Laurentian taxa Ceraurinus, Isotelus and Calyptaulax; deposits of eastern Laurentia are represented by temperate to cool-water carbonate facies (Wright & Stigall 2013). The highest diversities occur in the Chertkovskian and Baksian regional stages of the Siberian platform, with fewer taxa in the Dolborian and higher stages (correlation of Siberian stages and formations is based on Sennikov et al. 2015; Kanygin et al. 2017; Dronov 2017). Most species occur on the Siberian Platform (including the marginal areas of Taimyr) from the Chertovskian (Sa 1) to the Nirundian (Ka 4) but are also rarely found outside this area (Ormiston 1978; Ormiston & Ross 1979). On

the Kotelny Island of the New Siberian Islands, Evenkaspis occurs in the Chertovskian in sedimentary facies were similar to those on the Siberian Platform (Danukalova et al. 2015). Monorakos kledos from the Seward Peninsula in Alaska, United States, is one of the youngest species (Ka 3 or Ka 4, Dumoulin et al. 2014) and is found in the Alaska-Chukotka Microcontinent together with the Sandbian (Sa 1) Ceratevenkaspis sp. sensu Holloway (2004) from the Chukotka (alternatively Chukchi) Peninsula in the north-easternmost part of Siberia. Both the Altay terrane and the Hinggan area of northern China were considered peri-Siberian based on finds of Calyptaulax, Isotelus and Ceratevenkaspis from the Katian by Zhou & Zhen (2008). The Upper Ordovician of the Siberian platform is dominated by temperate to cool-water shelf carbonates, with the deposits of the Baksian and Dolborian regional stages representing high-energy carbonate ramp facies (Dronov 2017). This coincides with the highest abundance of monorakines on the Siberian platform in the Chertovskian-Baksian, with the peak in Taimyr coming in a little higher (middle to upper parts of the Tolmachev Formation) (Fig. 2). Only two monorakines occur higher up in the Taimyr succession, stratigraphically above the raphiophorid association. On the Siberian platform, a regional unconformity and transgressive surface can be traced at the base of the Mangazea sequence (Chertovskian Stage) (Dronov 2017). The wide geographical distribution of monorakines testifies to the closeness of these areas (Ormiston 1978; Ormiston & Ross 1979; Fortey & Cocks 2003; Holloway 2004), and Danukalova et al. (2015) even suggested that the Siberian Platform, the Taimyr Peninsula, New Siberian Island as well as the Chukotka area were part of the same, large shelf basin (Fig. 6).

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Scoto-Appalachian comparison The raphiophorid association in the Povorotnaya Formation includes an assemblage of trilobites belonging to the following genera: Ampyxella, Ampxyina, Failleana, Pararemopleurides, Raymondella, Remopleurides, Robergia, Stygina, Taimyraspis, Telephina and Toernquistia. It is early Katian in age (Ka 2). Several of these are new species, while others were named and described by Balashova (1959, 1960); a selection of trilobites is shown on Figure 3. All species require modern treatment, which is in progress. For present purposes, comparisons of generic assemblages with those elsewhere are generally sufficient for discussion. However, it is noted that the one genus which judging from the present literature might be considered endemic to Taimyr, Taimyraspis Balashova, 1959; has been revised from extensive new material, which shows that it is, in fact, likely to be a senior synonym of an Appalachian genus Effnaspis Dean, 1972; and closely related, if not identical to a Chinese genus, Yumenaspis Chang & Fan, 1960; which has been reported also from Scotland and Ireland (Tripp 1976; Owen et al. 1986; Ingham & Tripp 1991). Pararemopleurides has recently been named by Zhou et al. (2016) from the Pagoda Formation of the Yangtze Block, China. No genus in the raphiophorid association is endemic to Taimyr or the Siberian block. The fauna of the Povorotnaya Formation is identical in generic composition to many faunas following the course of the Caledonides, extending from Oklahoma along the Appalachian chain in United States, through western Ireland, Scotland, and further into Ordovician Baltica (Fig. 6). Later Ordovician faunas with such a distribution (excluding Baltica) have long been known from brachiopod and (to a lesser extent) trilobite literature as ‘Scoto-Appalachian’ (Webby et al. 2004). Such faunas are typical of the shelf seas marginal to the later Ordovician Laurentian palaeocontinent. They extend into areas now on the eastern side of the present Atlantic Ocean in Ireland and Scotland (Harper 1992; Fortey & Cocks 2003). The further similarities to faunas from Baltica reflect the progressive closure of the Iapetus Ocean in the Late Ordovician. Detailed comparisons can be made with the trilobite species from Taimyr from classical works describing the Appalachian trilobites (Cooper 1953; Whittington 1959) where the type species of Ampyxina and Raymondella were described; Effnaspis (= Taimyraspis) is from the same region. Typically, the Appalachian faunas were already present in the Darriwilian and found around much of the Laurentian epeiric seas (Chatterton & Ludvigsen 1976; Shaw & Fortey 1977; Hunda et al. 2003;

FOSSILS AND STRATA

Carlucci & Westrop 2012, 2015; Shaw 2014 and references therein). These faunas continue northwards (on present geography) into a series of Irish terranes marginal to Laurentia such as represented by the Raheen Formation, where a species closely related to Taimyraspis occurs (Owen et al. 1986), and thence across the Irish Sea into the Midland Valley terrane of Scotland. Very close comparisons can be made with a species of Bronteopsis from the Povorotnaya Formation with B. scotica Etheridge & Nicholson (= B. concentrica Linnarsson according to Skjeseth 1955) from the Balclatchie Formation, for example, while species of Ampyxina, Raymondella, Failleana and Toernquistia are also very close. Revisions and additions to these faunas by Tripp (1976, 1980, 1993) proved the similarity of Scottish faunas to contemporary Appalachian taxa; Tripp also summarized earlier literature. As far as Scandinavia is concerned, the Robergia species from the Povorotnaya Formation compares very closely with the type species R. microphthalma (Linnarsson, 1869), revised by Nikolaisen (1991). We also consider that Taimyraspis is related to the Norwegian genus Frognaspis Nikolaisen, 1965. Comparison of Ampyxella, Raymondella, Remopleurides and Toernquistia species can be made with Upper Ordovician Norwegian faunas described by Owen & Bruton (1980), Owen (1981) and Nikolaisen (1983). There is no doubt that the Povorotnaya Formation contains a suite of trilobites with a Scoto-Appalachian signature and opened up to migration to and from Baltica. We assume that the open shelf conditions on the Taimyr Peninsula were similar to those pertaining on the eastern fringes of the Iapetus Ocean, permitting the establishment of comparable faunas. Trinucleid trilobites are, however, lacking in our collections and those of Balashova (1959, 1960). Because Siberia (with Taimyr at its margin) is regarded as a separate palaeocontinent in the Ordovician (Torsvik & Cocks 2016) it may be the case that trinucleids were unable to reach Siberia, as they had limited capacity for dispersal, and tend to display endemicity in relation to palaeogeographical constraints. Connections of the Povorotnaya Formation fauna with those from upper Ordovician strata in central Asia and China are much less marked. Among the raphiophorids, Asian faunas include widespread specialized taxa with reduced numbers of thoracic segments, such as Taklamakania, which are not present among the diverse members of the same family in the Taimyr Ordovician. However, we have recognized the genus Pararemopleurides Zhou et al. 2016; which was recently described from the Pagoda Limestone of the Yangtze block, China, and also occurs in

FOSSILS AND STRATA

Kazakhstan. Zhou et al. (2016) also recognized a species of Effnaspis (i.e. Taimyraspis) from the Pagoda Limestone. Yumenaspis Chang & Fan, 1960, from the Chi Lien Mountains is also closely related to Taimyraspis. Both Remopleurides and Telephina are widespread in Ordovician strata that accumulated off continental platforms and are not critical in determining palaeogeography.

Barkov Formation The fauna of the Barkov Formation is slightly older and more limited in variety than that of the Povorotnaya Formation and includes abundant material of Ampyxoides, Robergia and Dionide species. The Robergia species is much like R. barrandii (Etheridge & Nicholson) from Girvan, Scotland, while the Dionide compares closely with the type species from Bohemia, Czech Republic. The Ampyxoides is a new species, but other members of the genus are Laurentian. The Dionide species is represented by a full suite of growth stages from probable meraspid stage that demonstrates a dramatic increase in the number of pygidial segments (and presumably ventral appendages) during growth. This may be an indication that some parts of the Barkov Formation accumulated under dysaerobic conditions, which is corroborated by the high organic content and alternating graptolite mudstone and siliceous limestone. Multiplication of thoracic and/or pygidial segments is known in the trinucleoids Alsataspididae (e.g. Seleneceme) and Dionididae, and this implies a similar multiplication of respiratory exites, which is consistent with enhanced oxygen respiration capacity as part of life in a low oxygen habitat. Fully grown trilobites of this kind lost the capacity to enrol because of a progressive mismatch of cephalon and pygidium and the modification of the thoracic segments to long (tr.) and thin. Hence, the environment of the Barkov Formation is probably more restricted than that of the Povorotnaya Formation, and this is reflected in the paucity of species. So far as they go, species comparisons are with the Scoto-Appalachian faunas, including other trilobites mentioned from the Povorotnaya Formation (i.e. odontopleurids, proetids, lichids and illaenids) but Dionide is much more widespread in the appropriate deep water biofacies.

Conclusions The Ordovician succession on the Taimyr Peninsula displays a contrast between a carbonate-dominated platform area to the south and a deeper, marginal

Trilobite biofacies, Late Ordovician of Taimyr

49

facies to the north. Trilobites have previously only been described from the southern facies and are known from around 50 species. The fauna is currently under revision with new material added, including also the deeper, more restricted environments to the north. It is clear that some species previously described from the Middle Ordovician Toll Formation compare with the Upper Ordovician Povorotnaya Formation, and comprise what we term the raphiophorid association, with taxa closely comparable to the Scoto-Appalachian faunas following the course of the Caledonides (Ampyxella, Ampxyina, Failleana, Pararemopleurides, Raymondella, Remopleurides, Robergia, Stygina, Taimyraspis, Telephina and Toernquistia). This deeper water, Late Ordovician fauna, was widely dispersed within a broad, low palaeolatitude belt, and therefore not strictly confined to the margin of a single plate. A similar distributional pattern was observed for the Ordovician graptolites of Taimyr (Sobolevskaya 2011). The second biofacies from Taimyr is termed the monorakinecheirurid-illaenid association and includes distinctive Late Ordovician taxa endemic to the Siberian Platform (the monorakines Carinopyge, Ceratevenkaspis, Elasmaspis, Evenkaspis and Monorakos), in association with genera more typical of Laurentia such as Cheirurus, Xylabion, Isotelus and Calyptaulax. These trilobites are associated with high energy, temperate to cool-water platform carbonates.

Acknowledgements We wish to thank Alan W. Owen and David L. Bruton for the possibility to contribute to this volume. A number of colleagues helped with Russian translations and/or literature, for which we are truly grateful (in alphabetical order): Andrey V. Dronov (Moscow), Elena Dunca (Uppsala), Alexander P. Gubanov (Uppsala), Mare Isakar (Tartu), Artem Kutchinsky (Stockholm), Nina Talyzina (Ume a), Tatiana Tolmacheva (St Petersburg), Olev Vinn (Tartu). Dr Dronov is also thanked for correcting Russian formation and geographical names in the present manuscript. Dr Rimma Sobolevskaya (St Petersburg) helped with, at that time, unpublished data on the stratigraphy along the Lower Taimyr River. Financial support for field work and study of the type collection in VSEGEI, St Petersburg, was through the SWEDARCTIC 1998 project awarded by Swedish Polar Research to David G. Gee (Uppsala). We are grateful for helpful comments by Frank Nikolaisen and an anonymous reviewer. This paper is a contribution to project IGCP 653 ‘The onset of the Great Ordovician Biodiversification Event’.

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FOSSILS AND STRATA Northeast. Sheet S-48 - Lake Taimyr (eastern part). Explanatory Letter, 19–40. Vserossijskij Naucno-Issledovatel’skij Geologiceskij Institut im. A.P. Karpinskogo (VSEGEI), Noril’sk. [in Russian]. Tesakov, Y.I., Predtechensky, N.N., Berger, A.Y., Khrojmkh, V.G., Kovalevskaya, E.O. & Sobolev, N.N. 1995: Stratigraphy of the Silurian of the Mountain Taimyr. In Simonov, O.N. & Malic, N.S. (eds): Nedra Tajmyra 1, 123–141. Vserossijskij NaucnoIssledovatel’skij Geologiceskij Institut im. A.P. Karpinskogo (VSEGEI), Noril’sk. [in Russian]. Tolmacheva, T.Y. 2003: Ordovician conodonts. In Sobolevskaya, R.F. (ed.): Atlas of the Paleozoic Fauna of Taimyr. Part 1, Brachiopods, Ostracods, Conodonts, 139–143. Vserossijskij Naucno-Issledovatel’skij Geologiceskij Institut im. A.P. Karpinskogo (VSEGEI), St. Petersburg. [in Russian]. Torsvik, T.H. & Andersen, T.B. 2002: The Taimyr fold belt, Arctic Siberia: timing of prefold remagnetisation and regional tectonics. Tectonophysics 352, 335–348. Torsvik, T.H. & Cocks, L.R.M. 2016: Earth History and Palaeogeography, 317 pp. Cambridge University Press, Cambridge. Tripp, R.P. 1976: Trilobites from the superstes Mudstones (Ordovician) at Aldon’s Quarry, near Girvan, Ayrshire. Transactions of the Royal Society of Edinburgh: Earth Sciences 69, 369–423. Tripp, R.P. 1980: Trilobites from the Ordovician Balclatchie and lower Ardwell groups of the Girvan District, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 71, 123– 145. Tripp, R.P. 1993: Review of the trilobites from the Middle Ordovician Barr Group, Girvan district, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 84, 87–102. Urvantsev, N.N. 1931: The Taimyr geological expedition of 1929. Trudi Glavnogo Geologo-Ravzvdocnogo V.S.N.H. SSSR 65, 1– 43. [in Russian]. Vernikovsky, V.A. 1996: The geodynamic evolution of the Taimyr folded area. Rossijska^a Akademi^a Nauk, Sibirskoe Otdelenie. Trudy Ob”edinennyj Institut Geologii, Geofiziki i Mineralogii 381, 1–252. [in Russian]. Vernikovsky, V.A. 1997: Neoproterozoic and late Paleozoic Taimyr Orogenic and ophiolitic belts, North Asia: a review and models for their formation. Proceedings of the 30th International Geological Congress, Beijing, China, 7, 121–138. Webby, B.D., Paris, F., Droser, M.L. & Percival, I. (eds) 2004: The Great Ordovician Biodiversification Event. Columbia University Press, New York, 484 pp. Whittington, H.B. 1959: Silicified Middle Ordovician trilobites: Remopleurididae, Trinucleidae, Raphiophoridae, Endymioniinae. Bulletin of the Museum of Comparative Zoology, Harvard University 121, 371–497. Wright, D.F. & Stigall, A.L. 2013: Geologic drivers of Late Ordovician faunal change in Laurentia: investigating links between tectonics, speciation, and biotic invasions. PLoS One 8, e68353. Zastrozhnov, D., Khudoley, A. & Verzhbitsky, V. 2014: The tectonic evolution of the Taimyr fold-thrust belt: history of studies and modern ideas. EGU General Assembly Conference Abstracts 16, EGU2014-13395. Zhang, X., Omma, J., Pease, V. & Scott, R. 2013: Provenance of Late Paleozoic-Mesozoic Sandstones, Taimyr Peninsula, the Arctic. Geosciences 3, 502–527. Zhou, Z.-Y. & Zhen, Y.Y. 2008: Trilobite-constrained Ordovician biogeography of China with reference to faunal connections with Australia. Proceedings of the Linnean Society of New South Wales 129, 183–195. Zhou, Z.-Q., Zhou, Z.-Y. & Xiang, L.-W. 2016: Trilobite fauna from the Ordovician Pagoda Formation of central and western Yangtze Block China CIP. China Publishing House, Beijing, 360 pp, 62 pls. Zlobin, M.N. 1956: Stratigraphy and facial features of the lower and middle Paleozoic of eastern Taimyr. Otchet po teme 122, Naucno-Issledovatel’skij Institut Geologii Arktiki (NIIGA), Leningrad. [in Russian].

FOSSILS AND STRATA Zlobin, M.N. 1958: The Taimyr Peninsula. In Beljaevsky, N.A. & Markovsky, A.P. (eds): Geologiceskoe stroenie SSSR. Tom I. Stratigrafi^a, 208–209. Gosgeoltehizdat, Moscow. [in Russian].

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Zonenshain, L.P., Kuzmin, M.I. & Natapov, L.M. 1990: Geology of the USSR: a plate-tectonic synthesis. American Geophysical Union Geodynamics Series 21, 1–242.

The earliest known West Gondwanan trilobites from the Anti-Atlas of Morocco, with a revision of the Family Bigotinidae Hup
e, 1953 GERD GEYER

Geyer, G. 2019: The earliest known West Gondwanan trilobites from the Anti-Atlas of Morocco, with a revision of the Family Bigotinidae Hup
e, 1953. Fossils and Strata, No. 64, pp. 55–153. The previously poorly investigated trilobite fauna of the upper Igoudine and lowest Amouslek formations in the western Anti-Atlas, Morocco, critical for the understanding of the earliest trilobites on a global scale, is studied in detail and its taxonomic diversity and biostratigraphical characteristics reviewed. The key section at Tiout, particularly the Tiout Member, yields surprisingly diverse faunal associations with trilobites of the families Bigotinidae and Fallotaspididae, of which only Hupetina antiqua, Eofallotaspis prima, E. tioutensis and Fallotaspis cf. F. tazemmourtensis have been previously identified. New genera and species from the Tiout section comprise Bigotina kelleri n. sp., B. monningeri n. sp., Issendalenia grandispina n. gen., n. sp., Tioutella floccofavosa n. gen., n. sp., Pseudobigotina antiatlasensis n. gen., n. sp., Eladiolinania castor n. gen., n. sp., E. pollux n. gen., n. sp., Debrenella larvalis n. gen., n. sp. and Fallotaspis antecedens n. sp. Bigotinops chouberti n. sp. is a new species from below the known range of Fallotaspis tazemmourtensis in the Amouslek section. A revision of other bigotinid genera and species from the Iberian sector of West Gondwana, Cadomian France, the Siberian Platform and the Altay-Sayan Foldbelt leads to a recombination of Bigotina angulata Suvorova, 1960; Eladiolinania? palaciosi Li~ n
an et al., 2008; E.? gordaensis Li~ n
an et al., 2008; Suvorovaella priva (Suvorova, 1960) and Suvorovaella? patria (Suvorova, 1960) and a suggested new family Minusinellidae. The previously established Eofallotaspis and Fallotaspis tazemmourtensis zones in the Moroccan biostratigraphical scheme are revised to become the Hupetina antiqua, Eofallotaspis tioutensis and Fallotaspis plana zones. □ Biostratigraphy, Lower Cambrian, phylogeny, Sibiria, Trilobita, West Gondwana. Gerd Geyer [[email protected]], Lehrstuhl f€ ur Geodynamik und Geomaterialforschung, Institut f€ ur Geographie und Geologie, Bayerische Julius-Maximilians-Universit€at W€ urzburg, Am Hubland 97074 W€ urzburg, Germany; manuscript received on 26/10/2017; manuscript accepted on 4/06/2018.

Introduction Trilobites from a pre-Fallotaspis tazemmourtensis Zone succession near Tiout, western Anti-Atlas, Morocco, were described in a preliminary report by Sdzuy (1978) and briefly dealt with in Sdzuy (1981). This interval was claimed to be not younger than the lowermost Atdabanian Stage on the Siberian Platform, which had been regarded to bear the oldest known trilobites on a global scale. These oldest trilobite-bearing strata at Tiout are dominated by essentially microbial carbonate rocks, which include abundant archaeocyaths and calcimicrobes (Debrenne & Debrenne 1978). The Tiout section (Fig. 1) has received additional importance by radiometric datings, carbon isotope studies and other stratigraphical methods performed directly on rocks from the section or on nearby sections (such as Oued Sdas; Fig. 1) that have more or less identical successions (Schmitt 1978, 1979a,b; Monninger

1979; Bertrand-Sarfati 1981; Latham & Riding 1990; Kirshvink et al. 1991; Magaritz et al. 1991; Landing et al. 1998, 2017; Maloof et al. 2005) so that the Tiout section can be regarded as an important reference section on a global scale (e.g. Compston et al. 1992; Maloof et al. 2010). The trilobite fauna from Tiout and the nearby Tazemmourt sections is critical for understanding the onset of the earliest trilobites and for the concept of the Cambrian Series 2 and Stage 3, but Sdzuy’s (1978) preliminary study only presented two new genera with in total three species: the bigotinid Hupetina antiqua and the fallotaspidids Eofallotaspis tioutensis and E. prima, without details on stratigraphical ranges and other potentially occurring trilobites in the sections. All trilobites from the relevant strata of the Tiout section and equivalent stratigraphical levels in the Tazemmourt and Amouslek sections of the western Anti-Atlas have been examined in the course of this study. The study presents the taxonomy and diversity of the trilobites and its

DOI 10.1002/9781119564232 © 2019 Lethaia Foundation. Published by John Wiley & Sons Ltd

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Fig. 1. Generalized geological map of southern Morocco showing Ediacaran–Cambrian rocks (medium grey), areas with Cambrian rocks (light grey) and outcrops of Neoproterozoic and Mesoproterozoic (Pan-African orogenic belt, crosses), with localities/sections relevant for this study (Tiout, Oued Sdas, Tazemmourt, Amouslek and Ouijjane) indicated. Trend of High-Atlas and Anti-Atlas ranges shown and major basement massifs named (Adrar n’Dren, El Graara, Jbel Sirwa, Jbel Ta€ıssa). Modified from Geyer (1989, fig. 1).

consequences for the biostratigraphy in the Souss Basin of southern Morocco. The trilobite faunas of the studied interval consist entirely of bigotinids and fallotaspidids, which provide clues for trilobite phylogeny in general and provincialism in particular. However, the implications for resolving the earliest trilobite phylogeny and the obvious close relationship between the bigotinids and fallotaspidids will be discussed in a separate study. Both groups may be characterized, for instance, by the intricate pattern of eye ridges with associated facial lines, obviously a primitive pattern of the earliest trilobites. The diverse Moroccan bigotinid fauna offers morphological data that contribute to a better understanding of the taxonomy within the family and suggests a re-evaluation of species described from Spain, northwestern France, the Siberian Platform and the Altay-Sayan Foldbelt.

Geological setting and stratigraphy of the Anti-Atlas sections This study is largely based on fossils collected in the western Anti-Atlas, Morocco. Stratigraphically significant specimens come from the Tiout,

Tazemmourt and Amouslek sections (Fig. 1), which have been characterized in some detail in earlier publications (e.g. Geyer et al. 1995; Geyer & Landing 2006), but critical data are provided below.

Tiout section The name ‘Tiout’ refers to a group of seven villages about 25 km southeast of Taroudannt. The central and most important of these villages is termed Igoudine and is located at the northern rim of the AntiAtlas where the roughly north–south trending ‘Tiout section’ ends (Fig. 2). The upper part of the section relevant for this study lies at ca. N 30°220 40″, W 8°410 20″. The Tiout section, composed of seven partial sections, stretches over a distance of more than 2 km. Its strata strike more or less west–east and dip at generally ca. 25–35° to the north. The total thickness of the studied sequence, including the Adoudou, Lie de vin, Igoudine and Amouslek formations, is about 1,700 m (Monninger 1979; Geyer 1989, 1990b; Geyer et al. 1995; Geyer & Landing 2006). It is the best studied and most referenced section of both the Moroccan Cambrian and, perhaps, the entire West Gondwanan palaeocontinent. The section gains its importance

FOSSILS AND STRATA

Fig. 2. Tiout section, western Anti-Atlas; aerial photographs of the northern end of the section with the course of the section and location of sampling horizons T1, T8, T14 and T17 indicated. Dolomite pattern indicates outcrop of the lower unnamed member of the Igoudine Formation, limestone (brick) pattern that of the Tiout Member, horizontal lines that of the Amouslek Formation. Satellite photographs © Google Maps.

from this documentation and favourable exposure, as well as easy accessibility. This type section of the Lie de vin Formation and the Igoudine Formation (including the Tiout Member) is an especially supreme example for the very shallow marine environmental conditions during the deposition of these units. Complex cyclicity and the conspicuous development of cyanobacterial-stromatolitic build-ups can be studied (e.g. Monninger 1979; Schmitt 1979a,b). Shelly fossils are rare below the Tiout Member, but the trilobite and archaeocyath faunas of the Tiout Member are fundamental for the lower part of the lower Cambrian biostratigraphy of the Atlas region. Igoudine Formation. – Although the Igoudine Formation (Geyer 1989, 1990b; Geyer & Landing 1995) is entirely dominated by massive limestones, it can be subdivided into two members, which clearly differ in facies. The lower, informal member (about 185 m in the section) consists of three subunits of carbonate rocks, which indicate restricted marine conditions during deposition, and the upper Tiout Member (about 115 m) is characterized by oolitic, intraclastbearing, or fossil hash limestones that indicate stronger wave action. The formation and its informal lower member commence with light and dark, thick-bedded, laminated micritic limestones and dolomitic limestones with large chert nodules. The overlying subunit consists of 70 m of massive, partly fetid, homogeneously black limestones with few dark chert nodules.

Earliest West Gondwanan trilobites

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Columnar stromatolites occur in three successive horizons near the middle of the subunit (Schmitt 1979a,b). The upper part shows small algal build-ups and a few simple trace fossils. This subunit includes a notable positive δ13C excursion (excursion B of Latham & Riding 1990), which has been correlated with the lower Atdabanian of the Siberian Platform (Kirshvink et al. 1991). The overlying 40 m of thick-bedded, light grey laminated dolostones constitute the ‘teepee-dolostone facies’ (Monninger 1979) or ‘pale dolostone facies’ (Schmitt 1979a). Shale intercalations are sparse, and argillaceous dolosiltites dominate (being almost absent in the subunit below). The highest subunit of the lower member has a thickness of about 30 m and is dominated by black limestones with bed thickness of up to a few metres. The highest thrombolite build-ups in the section are found towards the top of this subunit. Investigations revealed Hyolithellus tubes and poorly preserved, probable trilobite shell fragments from this subunit (Geyer et al. 1995). The trilobites relevant for this study come almost exclusively from the Tiout Member which forms the upper part of the Igoudine Formation (Figs 3, 4). The lower part of the Tiout Member consists of 20 m of ‘black oolitic limestone facies’ (Monninger 1979). The generally blackish, finely crystalline limestones are either oolitic or rich in intraclasts or oncolites. The interbeds are variably developed as olive, arenitic siltstones to mottled limestones. The base of the member is relatively sharp and placed at the lowest layer of arenitic calcareous siltstones. The oldest shelly fossils formally described so far from Morocco are trilobites from mottled limestone interbeds close to the base of the subunit (Hupetina antiqua from sample horizon T1; Figs 3, 4). About 13 m above, the first archaeocyaths occur in dark limestones (horizon Deb8; Debrenne & Debrenne 1978, 1995; Sdzuy 1978, 1981). Archaeocyaths become more frequent higher in the section in a rather distinctive facies of the upper part (about 90 m) of the Tiout Member. This second subunit of the Tiout Member is characterized by dark limestones with local intercalations of argillaceous and calcareous shales. Dark to light biohermal archaeocyath-bearing limestones may grade laterally into dark, oolitic limestones. The shales arc primarily developed as relief fillings; distinct bed–interbed alternations are not developed. Amouslek Formation. – Two hundred and sixty metres of strata representing the Amouslek Formation are exposed at the top of the Tiout section. The base of the formation is formed by a roughly

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Fig. 3. Lower part of the Tiout Member in the Tiout section, with location of several sampling sites indicated (see Fig. 4). Oblique view from south.

10-m-thick complex of hard, grey mudstones, overlain by an alternation of limestones and mudstones. Black, partly oolitic limestones alternate with thick units of greenish or grey, rarely purple, mudstones through most of the Amouslek Formation. Archaeocyaths are frequently found in the limestone beds, especially in the lower part, where they form local bioherms. The mudstones consist of argillaceous and calcareous siltstones with variable carbonate content. In contrast, the upper part of the preserved sequence is dominated by mudstones, and the few limestones form distinct marker beds. This mudstone-dominated part is partly rich in trilobites, with a typical Daguinaspis Zone assemblage.

Tazemmourt section The Tazemmourt section is located south of the village of Tazemmourt, about 10 km SSE of Taroudannt on the Taroudannt map sheet (N 30°230 45″, W 8°490 25″; Lambert coordinates 171.4/382.4). It lies on a marked northerly prolongation of the AntiAtlas. The rocks dip northward, and the top of the section at Tazemmourt is covered by alluvia of the Souss plain (Fig. 1). The base of the section about

2 km south of Tazemmourt is in an E-W-striking valley in the Igoudine Formation. Due to its accessibility, the Tazemmourt section received a great amount of interest in the first period of research on the Cambrian of the Anti-Atlas. It was the first section studied by Jean Abadie in 1949. Hup
e (1953a, 1959) completed more detailed studies on the trilobite faunas, which had first been dealt with in a preliminary paper by Hup
e & Abadie (1950). Fourteen holotypes of Hup
e’s trilobite species were selected from material from this section. The archaeocyaths have been described in detail by Debrenne (1960, 1964 and in Destombes et al. 1985). Nevertheless, the stratigraphical interval that is exposed in the section is fairly limited. Published sections (Abadie in Hup
e 1953a, 1959; Hollard in Destombes et al. 1985) differ considerably from each other, especially in the lower third of the section. Several faults cut through the succession and hamper the construction of a reliable bed-to-bed log. An overview of the Tazemmourt section with a generalized lithological sequence and biostratigraphy can be found in Geyer & Landing (2006, p. 61–64, fig. 11). The exposed sequence includes most of the Igoudine Formation and most of the Amouslek

Fig. 4. Upper part of the Igoudine Formation and basal part of the Amouslek Formation in the Tiout section illustrated as a lithological column with thickness in metres, lithostratigraphical and biostratigraphical subdivision and occurrences of the trilobites studied in this article. Biostratigraphical zones marked as interval zones starting at the lowest occurrence of the index species. Sdzuy’s (1978) horizons with trilobites are prefixed with ‘T’, the archaeocyath horizons of Debrenne & Debrenne (1978) with ‘Deb’. Lithological column modified from Monninger (1979). Filled squares indicate confident occurrences, open squares occurrences of material tentatively assigned to the species or forms. Abbreviations of lithologies: L, limestone; Larch, archaeocyath limestone; Lmott, mottled limestone; Loo, oolitic limestone; L/Ql, limestone–marlstone alternation; Q, marlstone; Qnod, nodular marlstone; Qs, silty marlstone; Sq, silty shale and marly siltstone. Samples with prefix ‘T’ refer to the sample horizons of K. Sdzuy, those with Deb to the archaeocyath sample horizons of F. Debrenne.

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Formation. The basal part includes the upper part of the Tiout Member and is the best example of that member apart from the Tiout section and the only succession except for that at Tiout known so far with a Hupetina antiqua assemblage.

Amouslek section The Amouslek section is located at the northwestern margin of the Anti-Atlas, about 32 km SW of Taroudannt on the A€ıt Baha map sheet (Lambert coordinates N 30°120 40″, W 9°20 5″; 150.6/362.7; Fig. 1). The succession is exposed in a few incomplete sections east and north of the nearby village (see Geyer et al. 1995, figs 7, 9). The upper part of the section includes outcrops that run for several hundred metres along a NNE-SSW-oriented ridge, about 1 km NNE of the village of Oumsdikt or Oumstegte (‘Amouslek’). The lower part of the section extends several hundred metres east of the village, with parts of the succession being well exposed at the slope northeast of the village. Amouslek is the classical section for the traditional Lower Cambrian in the Anti-Atlas. The trilobites and archaeocyaths from the section are among the most important for the biostratigraphy of the Atlas regions, and systematic studies were published by Hup
e (1953a) and Debrenne (1964; see also Debrenne & Debrenne 1995). Due to its easy accessibility, the locality has been visited during numerous field excursions and gained some interest by amateur and commercial fossil collectors more than a decade ago. As a consequence, the trilobites, which were primarily collected from shale units, became rarer, and good specimens are almost absent today. Nevertheless, Amouslek was chosen as the type locality for the Amouslek, Issafen and Asrir formations (Hollard in Destombes et al. 1985). A description of the Amouslek section with a generalized lithological sequence and biostratigraphy can be found in Geyer et al. (1995, pp. 63–73, figs 7– 10). The section starts with the upper part of the Lie de vin Formation. Boudda et al. (1979) indicated a thickness of the Igoudine Formation of 350–400 m (probably generalized values for the northwestern Anti-Atlas). The top of the Tiout Member of the Igoudine Formation was previously assigned to the ‘S
erie schisto-calcaire’ (or the ‘Slate-limestone formation’ of Hollard in Destombes et al. 1985), which is nearly synonymous with the Amouslek Formation. The Amouslek Formation in the section consists of shales with intercalated limestone beds, the latter primarily formed by archaeocyath–calcimicrobial bioherms. The formation can be subdivided into three

FOSSILS AND STRATA

lithological units, with a total thickness of about 220 m (the greatest thickness of the formation known so far). A lower unit is made up primarily of green slates, a middle unit of grey arenitic or reddish slates, and a thick upper unit of green and light yellow, argillaceous slaty shales (Hollard in Destombes et al. 1985; Geyer 1989; Geyer et al. 1995). However, the three units cannot be traced over long distances, and they are of minor lithostratigraphical significance. Some confusion results from the assumption that Georges Choubert located the oldest trilobites in the section in shales thought to lie below the ‘Fallotaspis Zone’, and Ahmed Boudda subsequently discovered additional trilobites in an isolated outcrop of the underlying limestones (Sdzuy 1978). Choubert’s trilobites were studied by Hup
e and left in repository with the assignment to a faunal horizon ‘F0’ indicating a position below the sample horizon ‘F1’. The latter can be identified within strata with Fallotaspis plana Hup
e, 1953, F. tazemmourtensis Hup
e, 1953 and the brachiopod Brevipelta chouberti Geyer, 1994 in green slates with occasional calcareous nodules in the lower unit of the Amouslek Formation. The presence of F. tazemmourtensis indicates the F. tazemmourtensis Zone. The new fauna from ‘F0’ occurs in green slates as well and consists almost exclusively of the bigotinid Bigotinops chouberti n. sp., with occasional valves of Brevipelta chouberti. The material was obviously collected from outcrop so that the location below horizon F1 can be taken as granted. A single slab exists in the collection, which was labelled ‘F0B’ by Hup
e, and this slab obviously from float yields a cranidium of Bigotinops chouberti, valves of Brevipelta chouberti, but also a number of relatively poorly preserved specimens of Fallotaspis cf. plana and F. cf. tazemmourtensis. It is thus more or less certain that this Bigotinops chouberti fauna from Amouslek comes from the base of the Amouslek Formation and from the Fallotaspis tazemmourtensis Zone rather than from a sub-tazemmourtensis level of the Tiout Member.

Trilobite occurrence, diversity and biostratigraphy The lowest occurrence of trilobites in the Tiout section (sample horizon T1; Figs 3, 4) lies almost immediately above the conspicuous facies change that marks the base of the Tiout Member. Above this horizon, trilobites have been detected in numerous layers, and a number of these horizons have produced determinable trilobites that feature a moderate diversity. The change in the composition of the trilobite associations reflects a phylogenetic

FOSSILS AND STRATA

development and serves for a refined biostratigraphical subdivision. The onset of trilobites in the section has been interpreted to be linked to favourable habitats and not to reflect phylogenetic development. However, shell fragments of trilobites and the Hyolithellus tubes mentioned above have been found in insoluble residues after dissolving limestone beds of the lower member of the Igoudine Formation. These findings indicate that the sudden occurrence of shelly fossils in the Tiout Member is most probably a preservational artefact (Geyer et al. 1995; Geyer & Landing 2006). The majority of the trilobite taxa found in the Tiout Member are bigotinids (Sdzuy 1978, 1981). Small fallotaspidids (species of the genus Eofallotaspis) occur less frequently, and the genus Eofallotaspis has been used to identify a sub ‘Fallotaspis Zone’ biostratigraphical unit (termed ‘Zone 0’ in Sdzuy 1978; Eofallotaspis Zone of Geyer 1990a). A preliminary report (Sdzuy 1978) established the new bigotinid genus Hupetina with the type species H. antiqua from the lowest trilobite-bearing horizon T1 and the new fallotaspidid genus Eofallotaspis with the species E. prima (from T4) and E. tioutensis (from T10). Sdzuy (1978, 1981) emphasized that Eofallotaspis is known from a number of horizons (T4, T9, T10, T12, T14 and T17). Lithostratigraphical and biostratigraphical correlation of these layers with equivalent strata of the Tazemmourt section and the identification of Hupetina antiqua from the Tazemmourt section in an equivalent position (Sdzuy 1978) prove the higher age of most of these strata (Sdzuy 1981 and G. Geyer, unpubl. data) compared with the Fallotaspis tazemmourtensis Zone, which previously was the oldest recognized zone in the traditional Moroccan biostratigraphical zonation (Hup
e 1952, 1953a; see discussions in Geyer 1990a). The present study indicates that Hupetina antiqua predates Eofallotaspis-bearing strata. In addition, Sdzuy’s (1978, 1981) generic concept of Eofallotaspis appears to have been influenced by the prevalence of small-sized fallotaspidid specimens. Sdzuy (1978) noted that the oldest Fallotaspis species of the Tiout section have been found in sample horizon T14, but the new species Fallotaspis antecedens described below represents a clear species of Fallotaspis that occurs in sample horizon T11, within the Eofallotaspis Zone and well below the Fallotaspis tazemmourtensis Zone. This detailed study indicates that three local biostratigraphical zones can be distinguished for the Tiout Member of the Igoudine Formation, termed the Hupetina antiqua, Eofallotaspis tazemmourtensis and Fallotaspis plana zones (Fig. 5).

Earliest West Gondwanan trilobites

61

Fig. 5. Biostratigraphical trilobite zonation established for the Moroccan Atlas ranges (middle column; Geyer 1990a; Geyer & Landing 1995, 2004) with the West Gondwanan chronostratigraphical standard series and stages (left column) and modifications suggested in this study (right column).

The Amouslek Formation of the Tiout section is biostratigraphically insufficiently characterized. Only the Daguinaspis Zone can be recognized with certainty at the top of the exposed sequence. However, lithological correlation with the nearby section of Tazemmourt permits a tentative bracketing of the underlying Choubertella and Fallotaspis tazemmourtensis zones. A small part of the section representing the Choubertella Zone and possibly the Fallotaspis tazemmourtensis Zone is presumably lacking because of two faults that cross the section. Li~ n
an & Sdzuy (1978) noted the presence of Lemdadella tioutensis and trilobites tentatively assigned to Bigotinops from the lowest ‘thick limestone above the base’ of the formation (see Fig. 4). Although no index fossil is known from these beds, these authors assigned the fauna to the Fallotaspis tazemmourtensis Zone and suggested the potential of the genus Lemdadella as an index fossil for the zone. Li~ n
an & Sdzuy’s (1978) suggestion is partly corroborated by

62

G. Geyer

the subsequent occurrence of Fallotaspis in the Tiout Member. However, the scattered occurrence of few specimens does not enable Lemdadella to be used as a reliable index fossil.

Trilobite preservation and preparation The overwhelming majority of trilobite specimens from the Tiout Member of the Igoudine Formation was obtained from carbonate rocks. The typical archaeocyath limestones are rich in fossils, particularly archaeocyath and calcimicrobes, whereas trilobites are relatively rare in this facies. They can be recognized as typical shepherd’s crook cross-sections but are nearly impossible to prepare in a way that allows recognition of large surfaces. A number of such trilobite remains from the archaeocyath limestone facies have been separated by leaching slightly silicified or dolomitized limestones, but poor remains are often difficult to determine with any certainty or to photograph. The extracted specimens are furthermore brittle in a way that they hardly survive their isolation from the residues. The majority of the specimens used in this study has been prepared from slightly marly intercalations between black oolitic limestones or archaeocyath limestones. These rocks with a considerably higher number of trilobite sclerites allow the typical shepherd’s crook cross-sections to be recognized during examination in the field, but also do not crack in a way that allows separation of specimens by conventional mechanical preparation. Klaus Sdzuy and his collaborators developed a special laborious procedure that allowed for the preparation of sufficiently preserved specimens for systematic studies: suitable samples were oven-heated and subsequently leached by dilute formic acid, which removed the calcareous shell material and calcareous particles in the matrix. Subsequent hardening by means of dilute cellulose varnish allowed cracking of the decalcified samples, from which silicone rubber and latex casts were taken. Unfortunately, the brittle nature of the decalcified samples caused a considerable number of specimens to be damaged or destroyed during removal of silicone casts. Nevertheless, about 200 specimens from carbonate samples of the Tiout Member were available for this study and constitute the major source for the recognizable biodiversity and the biostratigraphical framework. Specimens from the shale units from within the Tiout Member of Tiout, and the Amouslek Formation of the Tiout and Amouslek sections are generally

FOSSILS AND STRATA

dorsoventrally flattened and notably distorted. However, some of the specimens from the Amouslek section retained a morphology more or less similar to the original relief when the specimens are small and the matrix contains a small amount of calcareous matter.

Biostratigraphical implications and biochronological framework The Ediacaran–Cambrian cover of the Moroccan High-Atlas and Anti-Atlas ranges was deposited in the so-called Souss Basin (Geyer 1989). The axis of the basin roughly coincides with the presentday orientation of the Anti-Atlas. The lower part of the cover sequence has been subdivided into groups that reflect more or less asymmetrical transgressive–regressive cycles. Depositional environments changed through time with shoreline offlap and increasing influx of detrital material derived from the east. The general latest Ediacaran–Cambrian eastward extension of the basin leads to the fact that marine lowest and mid-lower Cambrian rocks are present only in the western part of the Souss Basin, and the outcrop conditions allow for a study of the oldest trilobite-bearing rocks only on the northern rim of the western Anti-Atlas. As a result, the Tiout, Tazemmourt and Amouslek sections (e.g. Geyer et al. 1995) are currently the only studied localities that provide data relevant for the oldest biostratigraphical zones. The trilobite-based, biostratigraphical framework for the Cambrian of the Anti-Atlas was originally proposed by Hup
e (1952, 1953a), and these publications can be considered to mark the beginning of modern lower Cambrian biostratigraphy. A later, partial revision of the zonal scheme (Hup
e 1960) was based to some extent on genera and species that were never formally established. New information, particularly on the Tiout Member at Tiout (Sdzuy 1978) and on the lower–middle Cambrian boundary interval, forced a revision of Hup
e’s (1952, 1953a, 1960) schemes (Geyer 1990a). This revised scheme includes the sub-Fallotaspis tazemmourtensis Zone trilobitebearing strata unified as the Eofallotaspis Zone. The occurrences of the trilobites in the Tiout Member of the Tiout section indicate three (local) biostratigraphical zones to be recognizable: the Hupetina antiqua, Eofallotaspis tazemmourtensis and Fallotaspis plana zones (Fig. 4). The occurrences of the trilobites indicate that the Hupetina antiqua and the Eofallotaspis tazemmourtensis zones are clearly distinguished. They are sufficiently discriminated in

FOSSILS AND STRATA

their faunal composition to expect them to be recognizable basinwide if the relevant strata are adequately fossiliferous. Archaeocyaths are commonly regarded as valuable index fossils for the lower Cambrian. Twenty-four horizons have been sampled in the Tiout Member of the Tiout section, with 19 of them listed to yield determinable species or forms (Debrenne & Debrenne 1978, 1995). A range chart assembled from the known data in Debrenne & Debrenne (1978, 1995) indicates a slight increase in the species-richness in the lower part of the member (sample horizons Deb3 to Deb15) that may be interpreted as an evolutionary development of the archaeocyath fauna. However, no further change is recognizable, and the assemblages do not allow a differentiation of archaeocyath zones in the member. Given the comparatively rich archaeocyath fauna with possibly up to 20 different species or informally determined forms (see Debrenne & Debrenne 1978, 1995), this fact suggests that the synchronous quite distinctive changes in the composition of the trilobite fauna reflect true evolutionary transformations that can be used for biostratigraphical units on a basinwide scale. Fallotaspis tazemmourtensis is a species with a limited number of specimens from the Tazemmourt and the Amouslek sections and from an imperfectly preserved specimen and the resulting caveat in the Tiout section. A much more common species is Fallotaspis plana. As discussed by Geyer (1996), the notes of Hup
e (1953a) and the labels on the type material indicate that Fallotaspis plana was known to him only from material said to be collected in the Fallotaspis tazemmourtensis Zone at Tazemmourt. However, cephalon GM Tr70 I (figured by Hup
e 1953a; pl. II, fig. 3) is partly covered by two valves of Brevipelta chouberti Geyer, 1994; a brachiopod species known previously only from the Choubertella and Daguinaspis zones with certainty. Additional material from the Jbel Ta€ıssa section came from the Choubertella Zone and the occurrence in the Fallotaspis tazemmourtensis Zone at Tazemmourt and Amouslek could not be proved when Geyer (1996) discussed the species. The stratigraphical range of Fallotaspis plana was consequently regarded as uncertain. New material studied from the Tiout section indicates the species to be present in the upper part of the Tiout Member in strata equivalent to the upper part of the former Eofallotaspis Zone and also in the Fallotaspis tazemmourtensis Zone. Fallotaspis plana and F. tazemmourtensis were to date the only species of Fallotaspis lacking an occipital spine as shown in Geyer (1996) and are otherwise similar in a number of aspects. Despite the range of

Earliest West Gondwanan trilobites

63

F. plana up into presumably the Daguinaspis Zone, it appears to be a more pragmatic way of creating a properly usable biostratigraphical zone to replace the F. tazemmourtensis Zone by an F. plana Zone. According to the available data, the base of this new F. plana Zone lies below the F. tazemmourtensis Zone. The top of the zone is defined by the onset of Choubertella, and this zonal boundary is not affected by the modification. F. tazemmourtensis can be used as an auxiliary index fossil for the F. plana Zone (Fig. 5). Recent investigation of volcanic ash layers in the Tiout section offers a highly precise U-Pb zircon geochronology for the upper Lie de vin through Amouslek formations and a temporal framework for the early trilobites studied herein (Landing et al. 2017). The data testify to rapid accumulation of the sediments of the upper Igoudine and lower Amouslek formations. An ash layer just at the base of the Amouslek Formation was dated at 519.23  0.14 Ma, another ash layer 34 m above – at 518.99  0.14 Ma (Landing et al. 2017). Sample horizon T1 with the earliest Hupetina antiqua specimens lies ca. 100 m above the prominent δ13C excursion in non-fossiliferous, restricted marine black limestones in the middle of the lower member of the Igoudine Formation. This strong carbon isotope excursion has been suggested to correlate with the IV excursion detected within the Repinaella Zone in the lower part of the Atdabanian Stage on the Siberian Platform (Landing et al. 2013). A ca. 522 Ma legacy date has been determined for a stratum 180 m lower in the Lie de vin Formation so that the δ13C excursion appears to have an estimated age of 521 Ma (Landing et al. 2017). A comprehensive discussion of the biostratigraphical issues that are brought up by the trilobite occurrences in the Tiout section and the other Moroccan localities, including a detailed discussion of the earliest trilobites from West Gondwana and its bearing on the earliest trilobites on a global scale, will be presented in a separate study.

Systematic palaeontology Material storage. – The material used in this study is in the repositories of the Mineralogisches Museum, Universit€at W€ urzburg (abbreviated MMUW), the Naturmuseum Senckenberg, Frankfurt (SMF), Museum National d’Histoire Naturelle, Paris (MNHN), the collection of the Mus
ee de G
eologie, Universit
e de Rennes 1, Rennes (IGR), the collection of the Service
G
eologique du Maroc, Ministere de l’Energie, des Mines et du D
eveloppement Durable, Rabat (SGM), the collection of the Palaeontological Institute, Russian

64

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Academy of Science, Moscow (PIN), and the collection of the Siberian Research Institute of Geology, Geophysics and Mineral Resources, Siberian Branch of the Russian Academy of Science, Novosibirsk (SNIIGGiMS), under the numbers provided in the material lists and figure captions. Terminology. – Terminology applied in the morphological descriptions follows that used in the revised trilobite volume of the Treatise on Invertebrate Paleontology (Whittington 1997). The term ocular line is used in a general way for all low ridges extending from or from near the eye lobes in the Fallotaspididae. The posterior ocular line is the low ridge extending from the posterior end of the eye lobe to the border and is located abaxially of the intergenal ridge. The term preocular facial line is used for a low ridge that extends from the eye ridge to the border furrow subparallel to, or at a slight angle to, the anterior section of the facial suture and is typical for the Bigotinidae (but also known from other taxa of the Redlichiina). The text distinguishes between Siberia, which is a geographical term for the present-day part of northern Asia, and Sibiria, used for the Cambrian continent composed of the Siberian Platform and the associated foldbelts.

Class Trilobita Walch, 1771 Order Redlichiida Richter, 1932 Suborder Redlichiina Richter, 1932 Family Bigotinidae Hup
e, 1953 [nom. transl. Sdzuy 1981; ex Bigotininae Hup
e, 1953a] Emended diagnosis. – Family of the Redlichiida with cephalon of relatively low tr. and sag. convexity, but with distinctly raised glabella, eye ridges and palpebral lobes. Glabella with three pairs of glabellar furrows that tend to fade in their expression forward, S1 vaguely bifurcate. Eye ridges well-developed, prominent, forming a unit with palpebral lobes that are barely differentiated from eye ridges; adaxial ends of eye ridges subdivided into several branches, the posterior of which are connected with the frontal lobe of the glabella, the anterior thread extended into a parafrontal band. Preglabellar field with a low swelling or a conspicuous plectrum that connects the front of the glabella with the anterior border.

FOSSILS AND STRATA

Anterior border narrow or moderately broad (sag.), raised above preglabellar field. Discussion. – The stratigraphical occurrence of the family Bigotinidae clearly indicates that the group is at the base of trilobite phylogeny and the Pararedlichiidae, Neoredlichiidae and other redlichioid groups are derived from the Bigotinidae. The family therefore belongs unmistakably to the Order Redlichiida Richter, 1932. A position within the Ptychopariida Swinnerton, 1915 was suggested by Jell & Adrain (2003) and has been followed in taxonomic compilations on the Internet (e.g. Fossilworks, http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_ no=155127; Arkhiv BVI, http://bvi.rusf.ru/taksa/ s0040/s0040000.htm). However, as the Bigotinidae is clearly an ancestor group of the Redlichiidae, either the Order Redlichiida is an invalid taxon or the assumption of Jell & Adrain (2003) and subsequent authors regarding a membership of the family Bigotinidae among the Ptychopariida is erroneous. The latter view is taken here. The genera of the Bigotinidae are characterized by a platform-type cephalon with a relatively low overall convexity, but with glabella, eye ridges, palpebral lobes and anterior border moderately to considerably elevated. All Bigotinidae possess a relatively simple glabella with slightly converging or subparallel lateral margins and three pairs of lateral glabellar furrows, which is a typical simple redlichioid pattern, combined with fused units formed by eye ridges and palpebral lobes that create a sort of fish-bone frame on the cranidium. The eye ridges are connected with the frontal lobe of the glabella in a more or less intricate manner and subdivided adaxially in a way that offers a key to the different genera of the family. In addition, the preglabellar field immediately in front of the glabella is generally occupied by a swelling which can be developed in different ways. The preglabellar field and the anterior cranidial border vary in breadth (sag.), but are generally narrow or of moderate width. Another typical feature of the Bigotinidae is the presence of a mostly low preocular facial line on the preocular areas close to the facial suture. It should be noted that this line is absent in all derived redlichioid genera, but offers a synapomorphy with the Fallotaspididae. The taxonomic subdivision of the family started with Bigotina Cobbold, 1935 and the recognition of a subgenus Bigotina (Bigotinella) Suvorova, 1960; which have served as taxa of convenience rather than coherent groupings for a number of species from Siberia, the Altay-Sayan Foldbelt and Australia (see below). Hup
e (1953a–c) recognized three genera from the Moroccan Anti-Atlas (Bigotinops, Ouijjania

FOSSILS AND STRATA

and Pruvostina). Hupetina Sdzuy, 1978 and Serrania Li~ n
an, 1978 completed the generic record until today. However, the trilobites described herein from the Moroccan Anti-Atlas and the consequent application of character sets suggest a revision of generic concepts and the introduction of a number of additional genera within the Bigotinidae. Minusinella Repina, 1960 (= Minusella Repina in Repina et al., 1964; see nomenclatorial remarks below) has been regarded as a genus of the Metadoxididae by Repina (e.g. Repina 1966, 1969) and most subsequent authors, but assigned to the Bigotinidae by other authors such as Sdzuy (1978) and Li~ n
an et al. (2008). The four species assigned to the genus are all characterized primarily by the frontal lobe of the glabella located so close to the anterior border that the preglabellar field is replaced by a narrow incision so that no plectrum or swelling is developed. The preocular areas slope relatively steeply anteriorly and ventrally so that the anterior border furrow is a narrow incision. The anterior border is formed by a relatively narrow blade with a steep posterior face inclined towards the border furrow. Due to the forward inclination of the eye ridges, the palpebral lobes in Minusinella (‘Minusella’) are slightly inclined to the eye ridges in lateral view. In addition, the eye ridges tend to grow in exsag. width adaxially. These differences are considered here to be of substantial significance, and Minusinella is regarded as representing a different family, for which the name Minusinellidae n. fam. is proposed herein (see below). Sdzuyia Li~ n
an & Gozalo, 1999 was assigned to the Bigotinidae and the Subfamily Serrinae by Li~ n
an et al. (2008) (see below). However, the genus clearly belongs to the Ellipsocephalidae as indicated by the arrangement and development of the palpebral lobes and eye ridges and their (lacking) extension towards the glabella. The revised concept includes the genera Bigotina, Hupetina, Serrania, Tioutella n. gen., Ouijjania, € Demuma Ozdikmen, 2008, Issendalenia n. gen., Eladiolinania n. gen. and Pseudobigotina n. gen. from the Cambrian West Gondwanan continent; and Bigotina, Bigotinella, Suvorovaella n. gen., and Elganellus Suvorova, 1958 from the Cambrian Sibirian continent. Elganellus is the most diverse genus from Sibiria, known from eight species described from the Siberian Platform and the Altay-Sayan Foldbelt. The genus is well characterized by its relatively narrow cranidium and eye ridges that are strongly rearwardly directed from near the glabellar front. Several of the species of Elganellus are in need of revision, but this is beyond the scope of the present study. The reason why the family is not known from other continents must be ascribed to two facts: its species were obviously short-lived and facies-bound. They are

Earliest West Gondwanan trilobites

65

confined to early trilobite-bearing strata and had already become extinct by the mid-Age 3, and they are almost exclusively distributed in shallow mixedcarbonate deposits. Such fossil-bearing strata are only known from West Gondwana, Sibiria and Laurentia, but the last of these continents appears to have been in a rather different faunal realm. The revised concept with a substantial number of genera and species emphasizes that the family has a far greater importance for the earliest trilobite phylogeny that hitherto accepted. Li~ n
an et al. (2008) introduced the Subfamily Serrinae within the Family Bigotinidae for the genera Hupetina Sdzuy, 1978; Serrania Li~ n
an, 1978, Sdzuyia Li~ n
an & Gozalo, 1999; and possibly Minusella Repina, 1960 (= Minusinella, see below). However, Sdzuyia and Minusinella are herein believed not to represent genera of the Bigotinidae as stated above. The diagnosis in Li~ n
an et al. (2008, pp. 127–128): ‘Bigotinid trilobites with arched eye ridge and palpebral lobe; librigenae with obtuse genal angle and a small sublateral spine. Thoracic axial ring (sag.) as wide as the pleural field, which is arched and presents an elliptical pleural furrow. Semielliptical micropygidium smaller than cranidium whit well-developed axis and pleurae’. (typological errors from the source) does not characterize a natural group. However, a subfamily that unites the genera Hupetina, Serrania, Pseudobigotina n. gen. and Eladiolinania n. gen. may prove to be a suitable taxon for a subdivision of the family, but is regarded as premature to date. In addition, the name ‘Serrinae’ is problematic under nomenclatural aspects. Li~ n
an et al. (2008, p. 127) emphasized that the name is intentionally used because the name ‘Serraninae’ was preoccupied for a subfamily of Recent fish. However, the correct name for the subfamily derived from the genus name Serrania would have been Serraniinae, which is not preoccupied. Alternatively, the name Hupetininae could have been chosen with equal qualification to avoid confusion. Genus Bigotina Cobbold, 1935

Type species. – Bigotina bivallata Cobbold, 1935, from the Saint-Jean-de-la-Riviere Formation, Saint-Jean-dela-Riviere, Normandy, France (originally monotypic). Emended diagnosis. – Cranidium with glabella variably of 60–75% cephalic length in adult individuals, frontal lobe slightly constricted or nearly as wide as width of glabella across L3, front subtruncate or with low curvature in dorsal view; occipital ring with small spine or prominent subterminal node; parafrontal band present, either running separately around front of

66

G. Geyer

glabella or fused with anterior margin of frontal lobe; anterior border moderately broad (sag.), arcuate, slightly to distinctly raised; preglabellar field with broad boss of variable expression; genal spine short and stout. Discussion. – The genus Bigotina Cobbold, 1935 is generally regarded as being paradigmatic for the Bigotinidae, and it indeed exhibits all features believed to be characteristic for the clade, that is a glabella with furrows that tend to fade forward, with S1 being slightly bifurcate; a homogenous lobe built by eye ridges and palpebral lobe; eye ridges that are longitudinally subdivided and diverge into three branches near the frontal lobe of the glabella and then forming a complicated pattern of threads; and a plectrum on the preglabellar field. It is more challenging to determine the generic characters and to distinguish the genus from others as indicated by the history of the genus. Ten species have been erected to date under Bigotina. These include (in alphabetical order): Bigotina angulata Suvorova, 1960; B. bivallata Cobbold, 1935; B. botomica Repina, 1966; B. coniferica Repina, 1960; Bigotina egregica (Repina, 1960); B. inornata Egorova, 1986; B. malykanica Suvorova, 1960; B. rara Repina, 1981; B. semirotunda Romanenko, 1980; B. tatei € (Woodward, 1884); and B. tina Opik, 1975. The type species, Bigotina bivallata Cobbold, 1935 from the lower Cambrian of western France, has been described several times (e.g. Pillola 1993). It is known from well-preserved specimens and can be used to characterize the genus appropriately. The critical characters include a glabella of fairly variable length with a frontal lobe that is nearly as wide as the glabella across L3 and with a subtruncate front. The parafrontal band is not fused with the front of the glabella, but shows a separate course winding around the front of the glabella. The preglabellar field is occupied by a broad boss, which is weakly defined laterally. The anterior border is comparatively broad (sag.) and almost flat in its profile. The anterior cephalic margin shows an almost regular arcuation. In addition, B. bivallata has a conspicuous surface sculpture consisting of dense

FOSSILS AND STRATA

granules of varying coarseness, with very coarse granules along the axis of the glabella. Some individuals, however, have a meshwork of fine- to medium-sized honeycombs on the glabella (see below). The two Australian species assigned to Bigotina, € B. tatei (Woodward, 1884) and B. tina Opik, 1975 are now recognized as species outside the bigotinids. Bigotina tatei from the upper lower Cambrian Parara Limestone, South Australia, is a species of the estaingiid genus Pararaia. It has a record of assignments to various genera, families and orders (introduced as Dolichometopus tatei Woodward, 1884 and assigned to Lorenzella by Kobayashi 1942). Bigotina tina € Opik, 1975; also from the Parara Limestone of South Australia, has been dealt with as Pararaia tina, but was assigned to Alanisia guillermoi (Richter & Richter, 1940), a species based on slightly distorted specimens from the Sierra Morena in Spain and subsequently reported from Australia on the basis of much better preserved material from the Yorke Peninsula, South Australia (e.g. Bengtson et al. 1990; Jell 1990). It needs to be emphasized again that this apparent match and the identification of the Australian material appears to be based on insufficient data and leads to an intercontinental correlation between Spain and Australia, and thus West Gondwana and East Gondwana, that is unreasonable as suggested by other data. A number of species were described from the Siberian Platform and from the Altay-Sayan Foldbelt. Bigotina (Bigotina) angulata Suvorova, 1960, also from the Sinsk ‘Horizon’ on the Lena River banks opposite the mouth of Malykan River, Yakutia, was characterized by Suvorova (1960) by a slightly angulate anterior margin of the anterior cephalic margin but this feature is based on the effect of incomplete removal of the matrix on the right hand side of the anterior margin of the specimen shown in Suvorova (1960, pl. II, fig. 21; see below). Pillola (1993) regarded the species as a synonym of Bigotina (Bigotinella) malykanica Suvorova, 1960. However, this view is not subscribed to here (see below).

Fig. 6. A–M, O–T, N?, Bigotina bivallata Cobbold, 1935. A, D, G, J, MMUW 2017B-003, small holaspid cranidium, dorsal view (A), detail of anterior glabella, eye ridges and parafrontal band (D), detail of median part of glabella and adjacent interocular area (G), and detail of surface with coarse granules with a central canal and tiny interspersed granules (J). B, E, H, MMUW 2017C-194, medium-sized holaspid cranidium, dorsal, anterior and lateral views. C, F, I, MMUW 2017C-195, large cranidium, dorsal, anterior and oblique lateral views. K, MMUW 2017C-196, incomplete meraspid cranidium, dorsal view. L, P, MMUW 2017C-197, medium-sized holaspid cranidium, dorsal views showing details of posterior glabella and occipital ring (L) with granulation around terminal node apparently related to occipital organ; and detail of anterior cranidium with well developed anteriorly tapering plectrum on preglabellar field (P). M, MMUW 2017C-198, early meraspid cranidium, dorsal view showing distinct bacculae. N, MMUW 2017C-199, partial holaspid cranidium with well-rounded frontal lobe and bifurcated lateral glabellar furrow S2, dorsal view. O, MMUW 2017C-200, incomplete meraspid cranidium, dorsal view. Q, MMUW 2017C-201, librigena, dorsal view. R, MMUW 2017C-202, early holaspid cranidium with prosopon of low irregular honeycomb polygons, dorsal view. S, MMUW 2017C-203, medium-sized holaspid cranidium with surface covered by low irregular honeycomb polygons, dorsal view. T, MMUW 2017C-204a and MMUW 2017C-204b, large cranidium with unusually broad glabella (right), dorsal view and early holaspid cranidium (upper left corner), oblique anterior view. All specimens from the Saint-Jean-de-la-Riviere Formation at the classical locality at the beach between Saint-Jean-de-la-Riviere and Saint-Georges-de-la-Riviere near Carteret, Normandy, northern France. All scale bars = 1 mm (corresponding to magnifications 5×, 7×, 10×, 15× and 20×, respectively).

FOSSILS AND STRATA

Earliest West Gondwanan trilobites

67

68

G. Geyer

Bigotina egregica Repina, 1960 comes from the Urits/Olekma ‘Horizon’ of the Mana River area in the East Sayan Range. The species was also identified from the Toyonian Parapoliella–Pseudoeteraspis Zone in the Angara Formation in drill cores of the Angara River region (Zharkov et al. 1990; Repina in Rozanov et al. 1992), together with a ‘Bigotina (Bigotina) sp. nov.’ (Zharkov et al. 1990, p. 95), but this determination must be regarded with caution. The species is characterized by a broadly subrectangular outline of the cranidium with a slender and relatively short glabella and a broad (sag.) preglabellar field. The species is certainly not a valid member of the Bigotinidae but appears to be related to genera such as Planaspis as already suggested by Pillola (1993). Bigotina (Bigotina) coniferica Repina, 1960 from the Ketemen ‘Horizon’ of the Altay-Sayan Foldbelt is very similar to Bigotina egregica. Repina (1966) considered that this species is identical with her B. (B.) egregica but Jell (2003) regarded it as a separate species. Bigotina (Bigotina) inornata Egorova, 1986 was described from the Pestrotsvet Formation at the Tolba River, Siberian Platform (Varlamov & Egorova 1986). The species falls a little out of the normal frame of Bigotina morphology in having a relatively strongly curved margin of the frontal lobe, short palpebral lobes and relatively strongly convex intraocular areas, but otherwise unites the typical Bigotina characters including a raised boss on the preglabellar field, a moderately broad (sag. and exsag.) and raised anterior border, and an occipital ring without a spine. Suvorova (1960) introduced a new subgenus Bigotina (Bigotinella). Her type species (and at that time only species), Bigotina (Bigotinella) malykanica Suvorova, 1960, is a species from the Atdabanian Pagetiellus anabarus Zone of the middle part of Pestrotsvet Formation on the Lena River, Yakutia. The diagnostic features identified by Suvorova are of little importance in the present concepts. As suggested by Pillola (1993), the holotype of Bigotina (Bigotinella) malykanica is a cranidium of a small and probably immature individual, and so are other specimens from the type lot. Pillola (1993) considered Bigotinella as a valid taxon and raised it to genus level. I concur with his opinion although for purely formal reasons as explained below (see under Bigotinella). Pillola (1993) suggested that Bigotina angulata Suvorova, 1960 should be considered a synonym of Bigotinella malykanica. He assumed that Bigotina angulata was based on adult specimens so that the differences are a result of differences in ontogenetic development (see material figured by Repina 1966, pl. XXIV, figs 9–14). However, it is highly improbable that the morphology seen in Bigotinella

FOSSILS AND STRATA

malykanica would have developed into the Bigotina angulata morphology as seen in the holotype. Particularly noteworthy is the equally tapering glabella with the faintly bulbous anterolateral corners of the otherwise subtruncate frontal lobe (see below). Bigotina (Bigotinella) botomica Repina, 1966 is a species originally assigned to Bigotinella. It was based on two cranidia recovered from the El’gyan ‘Horizon’ at Botoma River, Siberian Platform, and shares most characters with B. malykanica, but differs considerably in the anteriorly expanded glabella. This dilatation across L3 and the frontal lobe, however, is a result of lateral expansions of the glabellar lobes that run along the lateral margins of the glabella. Also characteristic for the species are faint glabellar furrows, narrow palpebral lobes and eye ridges, and a particularly narrow and distinctly elevated anterior border (see Repina 1966, pl. XXV, fig. 4) that distinguish it from true species of Bigotina and Bigotinella. Bigotina (Bigotinella) rara Repina in Repina & Luchinina, 1981; by contrast, does not match the typical characters seen in Bigotinella malykanica. The species comes from the lower Atdabanian Pagetiellus anabarus Zone of the middle part of the Pestrotsvet Formation in the middle Lena River area at the mouth of Malykan River, where it co-occurs with Bigotinella malykanica. Additional material is known from the Zhurynsky Mys section on the Lena River, where it co-occurs with Pagetiellus anabarus as well. The best preserved specimen, figured in Egorova et al. (1983, pl. 45, fig. 5), has a broad (sag.) occipital ring that extends into a robust occipital spine. The glabella is highly convex in transverse section, with a narrow curvature of the glabellar front, and conspicuously elevated, broad palpebral lobes and eye ridges. In addition, it has a strikingly narrow preglabellar field and a highly elevated anterior border (see also Varlamov et al. 2008, pl. 21, fig. 2). Bigotina (Bigotinella) semirotunda Romanenko in Pospelov & Romanenko, 1980 was described from the lower part of the Bograd ‘Horizon’, corresponding to the Atdabanian Stage of the Siberian Platform, from the Bol’shaya Kyrkala of the High Altay mountain range. The species is characterized by a wide glabella with considerably curved lateral margins, with a subtruncate frontal lobe, which almost reaches to the anterior border, eye ridge and palpebral lobe being separated by a distinct angulation, and by clearly convex intraocular areas. The species is difficult to assess but is regarded here as a member of a family outside the Bigotinidae. ‘Bigotina (Bigotinella) favosa Fed. (MS)’ is a nomen nudum used in Fedyanina (1973) for a trilobite listed to come from the Bograd ‘Horizon’ within a Resimopsis–Elganellus fauna in the Kuznetsk Alatau.

Glabella

Slightly tapered, margins straight, c. 75% ceph. length, 35–40% cranid. width

Margins straight, subparallel from L1 to L3, c. 75% ceph. length, 33–37% cran. width

Slightly tapered, margins straight, 77–83% ce. length, 30–37% cran. width

Slightly tapered, margins  straight, c. 77% ceph. length, c. 40% cran. width

Slightly tapered, margins  straight, 80– 85% ce. length, c. 40% cran. width

Species

Bigotina bivallata Cobbold 1935

Bigotina kelleri n. sp.

Bigotina angustifrons n. sp.

Bigotina angulata Suvorova 1960

Bigotina inornata Egorova, 1986

Cranidium

c. 70% width across L1, gently curved, fused with parafrontal band

c. 65% width across L1, subtruncate, fused with parafrontal band

c. 70% width acr. L1, subtruncate to bilobate, fused with parafrontal band

c. 60% width acr. L1, subtruncate to rounded, fused with parafrontal band

61–72% width across L1, subtruncate, not fused with parafrontal band

Frontal lobe

15–17% ceph. length, posterior margin with considerable curvature, with occipital node

15–18% ceph. length, posterior margin with low curvature, with occipital node 17–20% ceph. length, posterior margin moderately curved, with terminal. occipital node 13–16% ceph. length, posterior margin with low to mod. curvature, small occipital node 16–18% ceph. length, posterior margin with considerable curvature

Occipital ring

Relatively short, sl. oblique to axis, slight drop-shaped, not separated from eye ridge

Moderately long, sl. oblique to axis, not separated from eye ridge

Relatively long, alm. normal to axis, not separated from eye ridge

Moderately long, sl. oblique to axis, not separated from eye ridge Relatively short, sl. oblique to axis, slight kink to eye ridge

Palpebral lobe

Longitudinally subdivided, narrower than palpebr. lobe

Longitudinally subdivided, subequal to palpebr. lobe

Longitudinally subdivided, broader than palpebr. lobe

Not subdivided, broader than palpebr. lobe

Longitudinally subdivided, broader than palpebr. lobe

Eye ridge

Table 1. Summary of the morphological characters of the species of the Bigotinidae described in this study.

Shape of distorted parallelogram, without posterolateral extension, without swelling Shape of quarter ellipse, without posterolateral extension, small int. baccula

Shape of quarter circle, without posterolateral extension, small int. baccula

Shape of quarter circle, without posterolateral extension, small int. baccula

Subtrapezoidal, without posterolateral extension, small int. baccula

Intraocular area

Narrow, concave, with swelling growing anteriorly

Narrow, concave, with swelling

Mod. broad, concave, with obsol. low swelling

Mod. broad, concave, with low and wide plectrum

Mod. broad, almost flat, with low plectrum

Preglabellar field

Low arcuation

Distinct arcuation

c. 10–11% ceph. length, convex, subequal in width

c. 10% ceph. length, convex, subequal in width

8–10% cephalic length, convex, subequal in width

10–13% ceph. length, slightly convex, subequal in width

Low arcuation

Distinct arcuation

13–15% ceph. length, convex, subequal in width

Anterior border

Low arcuation

Anterior margin

(continued)

Unknown

Punctate

Probably smooth surface

Medium to coarse granulation, terrace ridges

Fine to coarse granulation

Surface ornament

FOSSILS AND STRATA Earliest West Gondwanan trilobites 69

Subparallel sides to slightly tapered, margins  straight, c. 80% ce. length, 30– 35% cranidial width Subparallel sides, margins slightly curved, 82–87% ce. length, c. 40% cranidial width

Subparallel sides, margins faintly indented, c. 82% ce. length, c. 40% cran. width

Slightly tapered, margins straight, 80% ceph. length, c. 38% cranidial width

Slightly tapered, margin straight, 76–83 ceph. length, 32–36% cran. width

Bigotina sp. A

Bigotinella malykanica (Suvorova 1960)

Bigotinops dangeardi Hupe, 1953

Bigotinops chouberti n. sp.

Bigotina sp. B

Glabella

Species

Cranidium

Table 1. (continued)

c. 65% width across L1, bilobatesubtruncate fused with parafrontal band c. 70% width across L1, subtruncate, semifused with parafrontal band 50–65% width across L1, subtruncate, semifused with parafrontal band

c. 65–75% width across L1, gently curved, fused with parafrontal band

c. 80–90% width gently curved, fused medially with parafrontal band

Frontal lobe 15–18% ceph. length, posterior margin with considerable curvature, with sm. occipital node 16–22% ceph. length, posterior margin with considerable curvature, with small occipital node 16–18% cephalic length, posterior margin, with moderate curvature 11% cephalic length, posterior margin with low curvature, with occipital node 16–21% ceph. length, posterior margin extended into occipital spine

Occipital ring

No clear longitudinal subdivision, subequal to palpebr. lobe

Moderately long, faintly oblique to axis, not separated from eye ridge Relatively short, oblique to axis, distinctly arcuate, slight kink to eye ridge Rel. short to mod. long, sl. oblique to axis, arcuate, not separated from eye ridge

Longitudinally subtriangular, without posterolateral extension and swelling

Shape of quarter circle, without posterolateral extension, without baccula Subtrapezoidal, with thin posterolateral extension, small int. baccula

Shape of quarter circle, without posterolateral extension, without baccula

Shape of quarter circle, without posterolateral extension, without baccula

Intraocular area

Narrow, with plectrum

Narrow, with distinct plectrum

Mod. broad, concave, with obsol. low swelling

Narrow groove, without recognizable plectrum

Broad, concave, without recognizable plectrum

Preglabellar field

Moderate arcuation

Low arcuation

9–13% ceph. length, convex, subequal in width

c. 8–10% cephalic length, convex, subequal in width

8–10% ceph. length, convex, subequal in width

c. 10% ceph. length, convex, subequal in width

Low arcuation

Low arcuation

c. 10% ceph. length, elevated, subequal in width

Anterior border

Moderate arcuation

Anterior margin

(continued)

Granulose or with irreg. reticulate pattern

Probably granulose

Coarsely punctate

Uncertain, probably smooth surface

Uncertain, probably smooth surface

Surface ornament

G. Geyer

Longitudinally subdivided, subequal to palpebr. lobe

Longitudinally subdivided, subequal to palpebr. lobe

No longitud. subdivision, subequal to palpebr. lobe

Longitudinally subdivided, subequal to palpebr. lobe

Eye ridge

Moderately long, oblique to axis, not separated from eye ridge

Relatively long, faintly oblique to axis, not separated from eye ridge

Palpebral lobe

70 FOSSILS AND STRATA

Glabella

Tapered forward, margins curved, 71–81% ceph. length, 36–43% cran. width

Clearly tapered, margins straight, 73– 77% ce. length, 37–39% cran. width

Slightly tapered, margins straight to faintly convex, 90–95% ceph. length, 35 –45% cran. width

Slightly tapered, sides straight, 81–86% ceph. length, 33–37% cran. width

Subcylindrical, margins straight or faintly curved, 85–89% ceph. length, c. 40% cran. width

Species

Ouijjania meridionalis Hupe, 1953

Demuma nicklesi (Hupe, 1953)

Hupetina antiqua Sdzuy 1978

Serrania verae Linan, 1978

Tioutella floccofavosa n. gen., n. sp.

Cranidium

Table 1. (continued)

c. 65% width across L1, subtruncate, not fused with parafrontal band

c. 50–55% width across L1, parabolic curvat., not fused with parafrontal band ca. 65% width across L1, narrow curvature, semifused with parafrontal band 70–80% width acr. L1, rounded to subtruncate, semifused with parafrontal band 65–75% width across L1, subtr., fused or semifused with parafrontal band

Frontal lobe

17–23% ceph. length, posterior margin with low to mod. curvature, without occipital node 14–18% ceph. length, posterior margin with moderate curvature, short occipital spine 16–18% ceph length, posterior margin relatively straight, without occipital node or spine

c. 13% cephalic length, posterior margin with moderate curvature, occipital node

c. 13% cephalic length, posterior margin with low curvature, occipital node

Occipital ring

Moderately long, slightly oblique to axis, faint angulation to eye ridge

Moderately long, distinctly oblique to axis, not separated from eye ridge Short, slightly oblique to axis, with sl. angulation to eye ridge

Moderately long, oblique to axis, angulation to eye ridge, thickened medially

Moderately long, oblique to axis, not separated from eye ridge

Palpebral lobe

Faint longitud. subdivision, slightly narrower than palpebr. lobe

Longitud. subdivided in prox. part, slightly narrower than palpebr. lobe

No longitud. subdivision, subequal to palpebr. lobe

Longitudinally subdivided, narrower than palpebr. lobe

Longitudinally subdivided, subequal to or broader than palpebr. lobe

Eye ridge

Shape of quarter circle, without posterolateral extension, without baccula

Shape of quarter circle, without posterolateral extension, small exterior baccula

Longitudinally subtriangular, without posterolateral extension, small exterior baccula Shape of oblique quarter circle, without posterolateral extension, with interior baccula Shape of quarter circle, without posterolateral extension, small exterior baccula

Intraocular area

Narrow to absent, groove-like

Narrow, with low plectrum

Narrow to absent, groove-like

Mod. broad, slightly concave, with low plectrum

Narrow, sunken, with faint swelling

Preglabellar field

Low arcuation

Distinct angulation

5–7% ceph. length, convex, growing in width toward suture

c. 17–19% cephalic length, slightly convex, red. in width toward suture 7–8% ceph. length, convex, of sub-equal width or growing toward suture 6–10% ceph. length, raised, convex, subequal in width

Low to moderate arcuation

Distinct angulation

17–19% ceph. length, convex, crescentic

Anterior border

Low to moderate arcuation

Anterior margin

Earliest West Gondwanan trilobites (continued)

Irregular polygons with low tubercles

Fine granulation

Most probably entirely smooth surface

With mediumsized granules (or punctate)

Unknown

Surface ornament

FOSSILS AND STRATA 71

Subcylindrical, margins straight, 85– 89% ce. length, c. 35% cran. width

Subcylindrical, margins straight or slightly constricted, c. 85% ce. length, c. 30% cran. width

Distinctly tapered, margins straight, c. 85% ceph. length, c. 45% cranidial width Tapered, margins straight or slightly curved, 73–78% ceph. length, 31–37% cran. width

Tapered, margins  straight, 76– 80% ce. length, c. 30% cran. width

Pseudobigotina inflata n. gen., n. sp.

Suvorovaella priva (Suvorova 1960)

Issendalenia grandispina n. gen., n. sp.

Eladiolinania inconspicua n. gen., n. sp.

Eladiolinania antiatlasensis n. gen., n. sp.

Glabella

Species

Cranidium

Table 1. (continued)

16–19% ceph. length, posterior margin with mod. to strong curvature, without occipital node 16–21% ceph. length, posterior margin with moderate curvature, with subterminal node

c. 25% ceph. length, posterior margin extended to occipital spine

15–19% cephalic length, posterior margin extended into short spine c. 15% ceph. length, posterior margin extends into terminal occipital spine

Occipital ring

Relatively long, sl. oblique to axis, not separated from eye ridge, rel. thin

Moderately long, sl. oblique to axis, not separated from eye ridge, rel. thin

Moderately long, slightly oblique to axis, dropshaped, angulate against eye ridge Moderately long, thick, very oblique to axis, faint angulation to eye ridge

Moderately long, oblique to axis, angulation to eye ridge

Palpebral lobe

No obvious subdivision, subequal to palpebr. lobe

No obvious subdivision, subequal to palpebr. lobe

Longitudinally subdivided, subequal to palpebr. lobe

Longitudinally subdivided, narrower than palpebr. lobe

No obvious subdivision, subequal to palpebr. lobe

Eye ridge

Shape of oblique quarter circle, without posterolateral extension, without baccula

Shape of oblique quarter circle, without posterolateral extension, with external baccula

Subtrapezoidal, without posterolateral extension, elevated

Shape of quarter circle, without posterolateral extension, distinctly convex Subtrapezoidal, without posterolateral extension, convex, sloping abaxially

Intraocular area

Broad, slightly concave, without clear swelling

Broad, concave, with low swelling

Moderately arcuate

Distinct angulation

Low arcuation

Low arcuation

Mod. broad, with moderately well developed plectrum Narrow to absent, groove-like

Low to moderate arcuation

Anterior margin

Narrow to absent, groove-like

Preglabellar field

c. 10% ceph. length, convex, subequal in width

9–12% ceph. length, convex, subequal in width

10–12% ceph. length, with low convexity, subequal in width

c. 9–10% cephalic length, convex, subequal in width

7–10% ceph. length, convex, subequal in width

Anterior border

(continued)

Apparently smooth

with fine to medium-sized granules

Most probably entirely smooth surface

Punctate

Most probably entirely smooth surface

Surface ornament

G. Geyer

c. 70% width across L1, gently curved, not fused with parafrontal band

c. 50% width across L1, subtruncate, semifused with parafrontal band c. 55% width across L1, narrow curvat., not fused with parafrontal band

Subequal width with L1, subtruncate or low curv., fused with parafrontal band