Phosphatic 'Inarticulate'
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A review of Cambrian lingulate brachiopods of England and Wales Paul Winrow Imperial College Department of Earth Sciences and Engineering PhD degree thesis 1 ABSTRACT The taxonomy of Cambrian lingulate (phosphatic shelled) brachiopods from England and Wales are reviewed in detail for the first time in nearly a century. 37 linguliformean brachiopod species, assigned to 23 genera, are described; 19 taxa are recorded in open taxonomy. Giving provisional names, three new genera, Svenjaella, Alexellus and Kayleigha are erected and nine new species are described (Chapter 4). Detailed cladistic analysis supports previous reports that Acrotretidae is a paraphyletic grouping of brachiopods which gave rise to other families within the Acrotretoidea (Chapter 6). Curticiidae is identified as lying outside the Acrotretoidea. The remaining families are supported as valid taxonomic units, albeit with some potential minor revisions. A new Scaphelasmatidae-Ceratretidae clade is consistently recovered. Support for the previously proposed subfamilies Neotretinae and Linnarssoniinae is partially recovered. The preservation of polygonal imprints of epithelial cells in lingulate brachiopods is reviewed and supplemented by new data (Chapter 7). The imprints are confirmed as representing moulds of epithelial cells as they are best preserved in areas where the shell has been thickened, and are similar in size to cells recorded in Lingula, the closest living relative to the extinct acrotretoids. Analysis of the morphology and sizes of cell-moulds demonstrates that there is no consistent relationship between cell width and valve size, and that they are not a useful taxonomic character within this group. The distribution of lingulate brachiopods across the Iapetus region is analysed using a number of statistical measures (Chapter 8). Although lingulate brachiopods have traditionally been considered to be of little utility in assessing palaeobiogeography, this analysis shows a clear palaeobiogeographic signal where lingulate faunas are sufficiently diverse, reflecting the history of the Iapetus ocean and the relative separation of Laurentia and Baltica through the Cambrian and Ordovician and provides confirmatory evidence that Palaeozoic lingulates had long-lived planktotrophic larvae. DISCLAIMER: This manuscript is produced only for examination as a doctoral thesis. It is not a publication in the sense of the International Code of Zoological Nomenclature. 2 DECLARATION OF ORIGINALITY I declare that all the work and findings contained in this thesis are the product of my own original research and writing, other than where appropriately referenced. ....................................................................... COPYRIGHT The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work 3 Contents 1 INTRODUCTION ....................................................................................................................... 10 Scope 10 Methodology 11 Acknowledgments 11 2 HISTORY OF CAMBRIAN LINGULATE BRACHIOPOD RESEARCH .......................... 12 th th 19 - 20 Century Research in Britain 12 Research in other areas 13 th st Late 20 to Early 21 Century Research 14 3 CAMBRIAN GEOLOGY OF ENGLAND AND WALES ...................................................... 16 Historical background to studies of Cambrian strata in Britain 16 The Cambrian timescale 16 British Cambrian timescale 17 Correlation of British Sequences 17 Palaeocontinental and tectonic Setting 20 Palaeogeography 22 Cambrian Successions and depositional environments in southern Britain 22 4 SYSTEMATIC PALAEONTOLOGY ...................................................................................... 23 5 PHYLOGENETICS OF LINGULATE BRACHIOPODS .................................................... 139 A brief history of Brachiopod classification 139 Impact of molecular studies on Brachiopod classification 145 Phylogeny and classification of Lingulate Brachiopods 147 6 CLADISTIC ANALYSIS OF ACROTRETOID BRACHIOPODS ..................................... 151 Introduction 151 Aims of this study 152 Methodology 152 Results 153 Discussion 157 Conclusions 161 7 EPITHELIAL CELL-MOULDS IN LINGULATE BRACHIOPODS ................................ 163 Introduction 163 Material and methods 165 New records of epithelial cell moulds from acrotretoid brachiopods 165 Discussion 169 4 Conclusions 174 Addendum: epithelial cell moulds in linguloid brachiopods ........................................................... 176 Introduction 176 Material 176 New records of epithelial cell moulds from linguloid brachiopods 176 Discussion 178 Conclusions 179 8 LINGULATE BRACHIOPODS AND THE LOWER PALAEOZOIC HISTORY OF THE IAPETUS OCEAN .............................................................................................................................. 181 Abstract 181 Introduction 181 Faunal evidence for the history of the Iapetus Ocean 183 Aims of this sudy 186 Methodology 186 Results 189 Discussion 196 Conclusions 198 REFERENCES .................................................................................................................................... 199 PLATES ............................................................................................................................................... 244 PLATE 1 245 PLATE 2 247 PLATE 3 249 PLATE 4 251 PLATE 5 253 PLATE 6 255 PLATE 7 257 PLATE 8 259 PLATE 9 261 PLATE 10 263 PLATE 11 265 PLATE 12 267 PLATE 13 269 PLATE 14 271 PLATE 15 273 PLATE 16 275 5 PLATE 17 277 APPENDICES ..................................................................................................................................... 279 Appendix 1: Summary of Cambrian successions in England and Wales 280 Appendix 2: List of specimens 293 Appendix 3: Characters used in cladistic analysis of acrotretoids 297 Appendix 4: Database of characters used in acrotretoid cladistic analysis 299 Appendix 5: Age ranges for taxa used in stratigraphic congruence analysis 303 Appendix 6: Consensus trees (all acrotretoid taxa) 306 Appendix 7: Consensus trees (excluding eoconulids) 311 Appendix 8: Stratigraphic congruence data for all trees (excluding eoconulids) 317 Appendix 9: List of specimens investigated with respect to preservation of epithelial cell-moulds in acrotretoid brachiopods 320 Appendix 10: Copyright permissions 321 6 List of figures Figure 1 British Cambrian stratigraphic correlation chart ....................................................................... 20 Figure 2 Palaeogeographic reconstruction at 540Ma .............................................................................. 21 Figure 3 Palaeogeographic reconstruction at 510Ma .............................................................................. 21 Figure 4 Stratigraphic range chart of lingulate brachiopods from the Cambrian of England and Wales 25 Figure 5 Images of O. parvus from Walcott (1908) ................................................................................ 39 Figure 6 Graph showing length:width plot of dorsal larval shells of Svenjaella parvus and Svenjaella minuta ...................................................................................................................................................... 43 Figure 7 Depiction of interior of ventral valve of Linnarssonia? comleyensis (taken from Cobbold, 1921). ...................................................................................................................................................... 81 Figure 8 Summary of brachiopod classification schemes (data from Williams et al 1996; 2000 and Carlson 2001) showing current classification on the left and others in chronological order ................ 140 Figure 9 Supra-ordinal classification of the Brachiopoda .................................................................... 144 Figure 10 Summary of family relationships in consensus tree IW10.................................................... 159 Figure 11 Plot showing min., max. and mean cell widths (ap = apical process, vf = valve floor) ........ 171 Figure 12 Graph showing relationship between mean cell width and valve width for British Cambrian lingulate brachiopods (based on data in Table 71). ............................................................................... 173 Figure 13 Epithelial cell moulds recorded in Cambrian Acrotretid brachiopods .................................. 175 Figure 14 Plot showing minimum, maximum and mean cell widths in linguloid brachiopods from the Cambrian of England and Wales ........................................................................................................... 178 Figure 15 Epithelial cell moulds recorded in Cambrian Linguloid brachiopods .................................. 180 Figure 16 Summary of Ordovician stratigraphic terminology used herein ........................................... 182 Figure 17 Similarity Indices for the Laurentia/Baltica palaeocontinent pair through the Cambrian and Ordovician ............................................................................................................................................. 190 Figure