Provided by the author(s) and NUI Galway in accordance with publisher policies. Please cite the published version when available. Title A Solution to Darwin's Dilemma: Differential Taphonomy of Ediacaran and Palaeozoic Non-Mineralised Discoidal Fossils Author(s) MacGabhann, Breandán Anraoi Publication Date 2012-08-29 Item record http://hdl.handle.net/10379/3406 Downloaded 2021-09-26T20:57:04Z Some rights reserved. For more information, please see the item record link above. A Solution to Darwin’s Dilemma: Differential taphonomy of Palaeozoic and Ediacaran non- mineralised discoidal fossils Volume 1 of 2 Breandán Anraoi MacGabhann Supervisor: Dr. John Murray Earth and Ocean Sciences, School of Natural Sciences, NUI Galway August 2012 Differential taphonomy of Palaeozoic and Ediacaran non-mineralised fossils Table of Contents List of Figures ........................................................................................................... ix List of Tables ........................................................................................................... xxi Taxonomic Statement ........................................................................................... xxiii Acknowledgements ................................................................................................ xxv Abstract ................................................................................................................. xxix 1. Darwin’s Dilemma ................................................................................................ 1 1.1 The non-mineralised fossils of the Ediacaran System ................................ 6 1.2 ‘Death Masks’ & ‘Gravity Casts’: preservation of the Precambrian fossils 11 1.3 Closure of a taphonomic window, or a mass extinction? .......................... 14 1.4 Exceptional preservation of non-mineralised fossils in the Phanerozoic .. 16 1.5 The Tafilalt Konservat Lagerstätte .......................................................... 18 1.6 Scope and aim of this project ................................................................... 18 1.7 Thesis plan ............................................................................................... 20 2. Analytical methods .............................................................................................. 21 2.1 Visual techniques and photography ......................................................... 22 2.2 Microscopy .............................................................................................. 25 2.2.1 SEM-EDS ......................................................................................... 26 2.2.2 Laser Raman ...................................................................................... 26 2.3 Geochemical techniques .......................................................................... 27 2.3.1 XRD .................................................................................................. 27 2.3.2 XRF ................................................................................................... 28 2.3.3 ICP-MS ............................................................................................. 28 3. Geological Context of Fossil Localities ............................................................... 31 3.1 Field locations .......................................................................................... 31 iii Breandán Anraoi MacGabhann 3.1.1 Morocco ............................................................................................. 31 3.1.1.1 Localities ..................................................................................... 34 M001 ........................................................................................................ 34 M003 ........................................................................................................ 38 M005 ........................................................................................................ 40 M008 ........................................................................................................ 45 M009 ........................................................................................................ 47 M010 ........................................................................................................ 47 M012 ........................................................................................................ 48 M020 ........................................................................................................ 49 3.1.2 United States of America ................................................................... 49 3.2 Geological context of additional fossil material ........................................ 50 3.2.1 United States of America ................................................................... 51 3.2.2 Australia ............................................................................................. 54 3.2.3 England .............................................................................................. 57 3.2.4 Ireland ................................................................................................ 57 3.2.5 Canada ............................................................................................... 59 4. The Class Eldoniata ............................................................................................. 63 4.1 Systematic Palaeontology ......................................................................... 66 Unranked stem-group CAMBROERNIDS Caron et al., 2010 ............................. 66 Class ELDONIATA class nov. ............................................................................ 66 Order ELDONIDA ord. nov. ............................................................................. 67 Family ELDONIIDAE Walcott, 1911 ................................................................ 68 Genus ELDONIA Walcott, 1911 ...................................................................... 68 ELDONIA LUDWIGI Walcott, 1911 .................................................................. 69 ELDONIA EUMORPHA (Sun and Hou, 1987) ................................................... 81 Family MAOYANIDISCIDAE nom. nov. ............................................................ 83 iv Differential taphonomy of Palaeozoic and Ediacaran non-mineralised fossils Genus MAOYANIDISCUS nom. nov. ................................................................ 84 MAOYANIDISCUS GRANDIS (Sun and Hou, 1987) .......................................... 85 MAOYANIDISCUS SP. ....................................................................................... 86 Genus PARAROTADISCUS Zhu, Zhao and Chen, 2002 .................................. 87 PARAROTADISCUS GUIZHOUENSIS (Zhao and Zhu, 1994) ............................. 88 ? Family MAOYANIDISCIDAE .......................................................................... 89 Genus VELUMBRELLA Stasińska, 1960 ........................................................... 89 VELUMBRELLA CZARNOCKII Stasińska, 1960 ................................................ 90 Genus SEPUTUS MacGabhann and Murray, 2010 .......................................... 91 SEPUTUS POMEROII MacGabhann and Murray, 2010 .................................... 91 Family PAROPSONEMIDAE fam. nov. .............................................................. 94 Genus PAROPSONEMA Clarke, 1900 .............................................................. 95 PAROPSONEMA CRYTOPHYA Clarke, 1900 ..................................................... 95 PAROPSONEMA MIRABILE (Chapman, 1926a) .............................................. 105 Genus PRAECLARUS gen. nov. ...................................................................... 110 PRAECLARUS VANROII sp. nov. ..................................................................... 111 PRAECLARUS SP. ........................................................................................... 117 Genus DISCOPHYLLUM Hall, 1847 .............................................................. 121 DISCOPHYLLUM PELTATUM Hall, 1847 ....................................................... 122 4.2 Other potential eldonides ...................................................................... 145 4.2.1 Eomedusa datsenkoi ........................................................................... 145 4.2.2 Sinoflabrum antiquum Zhang and Babcock, 2001 ............................ 146 4.2.3 ‘Trace fossils’ from Algeria ............................................................... 146 4.2.4 Astropolichnus hispanicus Crimes et al., 1977 ..................................... 147 4.3 General remarks ..................................................................................... 148 4.3.1 Eldonide phylogeny ......................................................................... 148 4.3.2 Palaeoenvironmental tolerance of the eldonides .............................. 151 v Breandán Anraoi MacGabhann 4.3.3 Stratigraphic range of the eldonides ................................................. 151 5. Taphonomy ........................................................................................................ 153 5.1 Taphonomy of the Burgess Shale and Eldonia ludwigi ........................... 160 5.1.1 Previous Research ............................................................................. 160 5.1.2 Taphonomy of Eldonia ludwigi from the Burgess Shale ................... 167 5.2 Taphonomy of the Tafilalt paropsonemids