DOCSLIB.ORG

Segmentation and Oxygen Diffusion in the Ediacaran Dickinsonia: an Applied Analysis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Segmentation and Oxygen Diffusion in the Ediacaran Dickinsonia: an Applied Analysis Journal and Proceedings of the Royal Society of New South Wales, vol. 147, nos. 453 & 454, pp. 107-120. ISSN 0035-9173/14/020107-14 Segmentation and Oxygen Diffusion in the Ediacaran Dickinsonia: an Applied Analysis Brett Gooden1 1Wellington Caves Fossil Studies Centre, 89 Caves Road, Wellington, NSW 2820, Australia E-mail: [email protected] Abstract Many Ediacarans are constructed of multiple parallel segments. Two forms of segment were analysed in the present study, a cylindrical and cuboidal form. The theoretical surface area to volume (A/V) ratio of a structure composed of cylindrical segments is twice that of one composed of cuboidal segments of the same thickness. In this analysis the Ediacaran Dickinsonia was assumed to be a bottom-dwelling marine animal. Individual A/V ratios were calculated for 60 fossil specimens of Dickinsonia of known thickness and diameter assuming either a structure composed of tapering cylinders (conical frusta) or tapering cuboids (square frusta). With increasing body diameter a lower limit of the A/V ratio was approached in both structural forms at a body diameter of approximately 50 millimetres. The segments were assumed to contain solid connective tissue. The theoretical oxygen concentration gradient due to simple diffusion into both forms was calculated and the effect of a collagenous segmental wall on these gradients was determined. The cylindrical form with a collagenous wall was found to be viable within the constraints of this analysis but not the cuboidal form. The findings support the hypothesis that Dickinsonia could have obtained adequate oxygenation by simple diffusion with cylindrical but not cuboidal segments. Keywords Dickinsonia, Ediacarans, segmentation, oxygen diffusion. Introduction The characteristic surface feature of many In 1964 Berkner and Marshall hypothesised species of Ediacaran is a repeated parallel that the trigger for the emergence of segmentation. In 1989 Seilacher suggested metazoans was the appearance of oxygen in that a wide range of Ediacarans including the atmosphere. Since then the estimated Pteridinium and Dickinsonia had a common oxygen content of the Precambrian structural form composed of parallel atmosphere has progressively increased chambers underlying the defining surface (Butterfield, 2009; Canfield, 2007; Shields- segmentation (Figs. 1, 2 and 3). He Zhou, 2011), which raises once more the represented these chambers as essentially vexed question of the relationship between cuboidal in shape. Grazhdankin (2002) the structure and the mode of oxygen drew these chambers as purely box-like or delivery in the Ediacaran biota (Raff, 1970; cuboidal in form with square cross section. Runnegar, 1982). 107 JOURNAL AND PROCEEDINGS OF THE ROYAL SOCIETY OF NEW SOUTH WALES Gooden – Oxygen Diffusion in the Ediacaran Dickinsonia (2009) modelled Pteridinium on the basis of a cuboidal structure in order to analyse the A/V ratio. However illustrative material presented by Jenkins (1992) raised the possibility that the segments in Pteridinium may have been more cylindrical than cuboidal in shape and recent photographic evidence lends further support to this concept (Elliott, 2011). Figure 3: Schematic diagram of Dickinsonia lying on the biomat covering the ocean floor (dark grey shaded area) showing a section through a tapering cylindrical segment and diffusion paths LM of thickness 1.6 mm adjacent to the periphery and NP Figure 1: Fossil of Dickinsonia. Scale in centimetres of thickness 0.8 mm adjacent to the midline. (South Australian Museum, specimen No. P49355). Recently Retallack (2012) has suggested that some Ediacarans including Pteridinium and Dickinsonia were terrestrial organisms similar to lichens. Though the matter is clearly contentious, it would appear that the generally held view at the present time is that the Ediacarans were marine organisms (Switek, 2012) and for the purposes of the present palaeo-physiological analysis the author has assumed that to be the case. The first objective of the present study was to analyse theoretically the A/V ratio of two Figure 2: Fossil of Pteridinium. Scale in hypothetical structural forms, one centimetres (specimen by courtesy of Dr Jim Gehling, composed of purely cylindrical segments South Australian Museum). and the other of purely cuboidal segments. These ratios were then applied to data from The surface area to volume (A/V) ratio is actual fossil specimens of Dickinsonia in critical for the survival of marine organisms which the profile thickness and diameter that are dependent solely on the diffusion of were known. In this way the A/V ratio of oxygen from a watery environment through each specimen could be calculated for either their surface and into their living tissue a purely cylindrical or cuboidal form of (Krogh, 1941; Alexander, 1971). Laflamme segmentation and compared. Finally. the 108 JOURNAL AND PROCEEDINGS OF THE ROYAL SOCIETY OF NEW SOUTH WALES Gooden – Oxygen Diffusion in the Ediacaran Dickinsonia theoretical oxygen concentration gradient in segment exposed to the external cylindrical and cuboidal segments was environment, Vcub is the volume of the calculated and considered in relation to the segment and x is half the length of a side of possible viability of each structural form. the square cross section (Fig. 5). Methods Factors affecting the A/V ratio Ratio of diametrical length to arc length Consider a section composed of n Figure 5: Cylindrical and cuboidal segments. semicircular arcs, then Lateral view. Shaded area indicates surface in contact with external watery environment. l a/l d = n. π. r/ n.2. r = π/2 (1) A/V ratio of a cylindrical segment where la is the total arc length of the section, ld is the total diametrical length of the Consider a hypothetical cylindrical segment section and r is the radius of an arc (Fig. 4). of the length L. Rearranging Eq. 1 la = ld . π/2. 2 Acyl/Vcyl = π 2x L/π x L = 2/x (3) Therefore rolling a section of n arcs flat increases its diametrical length by a factor of where Acyl is the surface area of the 1.57 times (see Fig. 8B). cylindrical segment exposed to the external environment, Vcyl is the volume of the cylindrical segment and x is the radius of the cylinder (Fig. 5). A/V ratio of a hypothetical Dickinsonia constructed of tapering cuboidal segments Figure 4: Portion of a section of n semicircular arcs of radius r. The arc length is π/r and the diametrical length is 2r, hence the ratio of the arc length to the diametrical length is π/2. Figure 6A: Tapering cylindrical (conical frustum) and tapering cuboidal (square frustum) segments. A/V ratio of a cuboidal segment With reference to points A and B, see Fig. 11 and Consider a hypothetical cuboidal segment 12. with square cross section and length L. 2 2 ADtcub/VDtcub = 2 π R /π R 2x = 1/x (4) 2 Acub/Vcub = 4 x L/4 x L = 1/x (2) where ADtcub is the surface area of a tapering where Acub is the surface area (upper plus cuboidal segment (square frustum), (upper lower surfaces only) of the cuboidal plus lower surfaces only) exposed to water, 109 JOURNAL AND PROCEEDINGS OF THE ROYAL SOCIETY OF NEW SOUTH WALES Gooden – Oxygen Diffusion in the Ediacaran Dickinsonia VDtcub is the volume of the segment, R = beginning to the end of the diffusion half the mean overall diameter of the distance ∂x. Dickinsonia and x = half the mean thickness of the Dickinsonia (Fig. 6A and B). The maximum diffusion distance for oxygen in a cuboidal segment of connective tissue s = C02DCT / MCT (Warburg, 1923; Alexander, 1971) (7) where s = half the thickness in millimetres (mm) of a viable cuboidal segment of connective tissue in which oxygen diffuses Figure 6B: Portion of the cross section of a from both upper and lower surfaces, Co = hypothetical Dickinsonia constructed of either the difference in oxygen concentration, cylindrical or cuboidal segments. expressed as a fraction of one atmosphere, from either surface of the segment to half A/V ratio of a hypothetical Dickinsonia its thickness where the oxygen constructed of tapering cylindrical segments concentration falls to zero, DCT = the 2 2 ADtcyl/VDtcyl = (π R) / (π R) x/2 = 2/x (5) diffusion coefficient of oxygen in connective tissue in millilitres (ml) of where ADtcyl is the surface area of tapering oxygen diffusing per cubic centimetre of cylindrical segment (conical frustum) surface area per minute at a pressure exposed to water and VDtcyl is the volume of gradient of one atmosphere per centimetre -4 the segment. R and x as in (4) (Fig. 6A and of tissue thickness (= 0.11 x 10 ), MCT = B). the rate of oxygen consumption of connective tissue in ml of oxygen per gram Note: This hypothetical calculation assumes of tissue per minute (=1/600). that there is no loss in surface area of a cylindrical segment at the junctions between The maximum diffusion distance for oxygen segments (see Discussion). in a cylindrical segment of connective tissue = Factors affecting the rate of diffusion r C0 4DCT / MCT of oxygen (Fenn, 1927; Alexander, 1971) (8) Fick's first law where r = maximum radius of a viable ∂v/∂t = A. D. ∂c/∂x (Prosser, 1961) (6) cylinder of connective tissue in mm, Co = the difference in the oxygen concentration, where ∂v/∂t = volume of oxygen ∂v that expressed as a fraction of one atmosphere, diffuses in time ∂t, A = the area of the from the surface of the cylindrical segment surface across which the oxygen diffuses to its central axis where the oxygen into the tissue , D = the diffusion concentration falls to zero. DCT and MCT as coefficient of oxygen in the tissue, ∂x = the in (7). distance the oxygen diffuses into the tissue and ∂c = the concentration gradient of oxygen in the tissue, that is, the difference in the oxygen concentration from the 110 JOURNAL AND PROCEEDINGS OF THE ROYAL SOCIETY OF NEW SOUTH WALES Gooden – Oxygen Diffusion in the Ediacaran Dickinsonia Source of data for the analysis of connective tissue.
Load more

Recommended publications
  • Ediacaran) of Earth – Nature’S Experiments
    The Early Animals (Ediacaran) of Earth – Nature’s Experiments Donald Baumgartner Medical Entomologist, Biologist, and Fossil Enthusiast Presentation before Chicago Rocks and Mineral Society May 10, 2014 Illinois Famous for Pennsylvanian Fossils 3 In the Beginning: The Big Bang . Earth formed 4.6 billion years ago Fossil Record Order 95% of higher taxa: Random plant divisions domains & kingdoms Cambrian Atdabanian Fauna Vendian Tommotian Fauna Ediacaran Fauna protists Proterozoic algae McConnell (Baptist)College Pre C - Fossil Order Archaean bacteria Source: Truett Kurt Wise The First Cells . 3.8 billion years ago, oxygen levels in atmosphere and seas were low • Early prokaryotic cells probably were anaerobic • Stromatolites . Divergence separated bacteria from ancestors of archaeans and eukaryotes Stromatolites Dominated the Earth Stromatolites of cyanobacteria ruled the Earth from 3.8 b.y. to 600 m. [2.5 b.y.]. Believed that Earth glaciations are correlated with great demise of stromatolites world-wide. 8 The Oxygen Atmosphere . Cyanobacteria evolved an oxygen-releasing, noncyclic pathway of photosynthesis • Changed Earth’s atmosphere . Increased oxygen favored aerobic respiration Early Multi-Cellular Life Was Born Eosphaera & Kakabekia at 2 b.y in Canada Gunflint Chert 11 Earliest Multi-Cellular Metazoan Life (1) Alga Eukaryote Grypania of MI at 1.85 b.y. MI fossil outcrop 12 Earliest Multi-Cellular Metazoan Life (2) Beads Horodyskia of MT and Aust. at 1.5 b.y. thought to be algae 13 Source: Fedonkin et al. 2007 Rise of Animals Tappania Fungus at 1.5 b.y Described now from China, Russia, Canada, India, & Australia 14 Earliest Multi-Cellular Metazoan Animals (3) Worm-like Parmia of N.E.
    [Show full text]
  • Mcmenamin FM
    The Garden of Ediacara • Frontispiece: The Nama Group, Aus, Namibia, August 9, 1993. From left to right, A. Seilacher, E. Seilacher, P. Seilacher, M. McMenamin, H. Luginsland, and F. Pflüger. Photograph by C. K. Brain. The Garden of Ediacara • Discovering the First Complex Life Mark A. S. McMenamin C Columbia University Press New York C Columbia University Press Publishers Since 1893 New York Chichester, West Sussex Copyright © 1998 Columbia University Press All rights reserved Library of Congress Cataloging-in-Publication Data McMenamin, Mark A. The garden of Ediacara : discovering the first complex life / Mark A. S. McMenamin. p. cm. Includes bibliographical references and index. ISBN 0-231-10558-4 (cloth) — ISBN 0–231–10559–2 (pbk.) 1. Paleontology—Precambrian. 2. Fossils. I. Title. QE724.M364 1998 560'.171—dc21 97-38073 Casebound editions of Columbia University Press books are printed on permanent and durable acid-free paper. Printed in the United States of America c 10 9 8 7 6 5 4 3 2 1 p 10 9 8 7 6 5 4 3 2 1 For Gene Foley Desert Rat par excellence and to the memory of Professor Gonzalo Vidal This page intentionally left blank Contents Foreword • ix Preface • xiii Acknowledgments • xv 1. Mystery Fossil 1 2. The Sand Menagerie 11 3. Vermiforma 47 4. The Nama Group 61 5. Back to the Garden 121 6. Cloudina 157 7. Ophrydium 167 8. Reunite Rodinia! 173 9. The Mexican Find: Sonora 1995 189 10. The Lost World 213 11. A Family Tree 225 12. Awareness of Ediacara 239 13. Revenge of the Mole Rats 255 Epilogue: Parallel Evolution • 279 Appendix • 283 Index • 285 This page intentionally left blank Foreword Dorion Sagan Virtually as soon as earth’s crust cools enough to be hospitable to life, we find evidence of life on its surface.
    [Show full text]
  • EDITORIAL NOTE Collection of Paleontology Papers in Honor of The
    Anais da Academia Brasileira de Ciências (2019) 91(Suppl. 2): e20191434 (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690 http://dx.doi.org/10.1590/0001-3765201920191434 www.scielo.br/aabc | www.fb.com/aabcjournal EDITORIAL NOTE Collection of Paleontology Papers in honor of the Centenary of the Brazilian Academy of Sciences ALEXANDER W.A. KELLNER* and MARINA B. SOARES Laboratório de Sistemática e Tafonomia de Vertebrados Fósseis, Departamento de Geologia e Paleontologia do Museu Nacional/UFRJ, Quinta da Boa Vista, s/n, São Cristóvão, 20940-040 Rio de Janeiro, RJ, Brazil How to cite: KELLNER AWA AND SOARES MB. 2019. Collection of Paleontology Papers in honor of the Centenary of the Brazilian Academy of Sciences. An Acad Bras Cienc 91: e20191434. DOI 10.1590/0001-3765201920191434. The Brazilian Academy of Sciences is a non-profit organization (ABC 2019) that has completed one century of existence in 2016. A series of special publications was organized by the Annals of the Brazilian Academy of Sciences (AABC) in celebration of this important date (e.g., Kellner 2017, Crespilho 2018, Cavaleiro 2018). Here we have the pleasure to introduce the final of these volumes gathering 20 original contributions in paleontology, the science dedicated to the study of all evidences of life that have been preserved in layers of deep time. The topics presented here vary from the description of new species and specimens of flying reptiles, dinosaurs, and crocodylomorphs to studies on biogeography, osteohistology, and specific contributions provided by microfossils. Over 70 authors from different countries were involved in this volume, showing the increasing international integration of Brazilian paleontologists.
    [Show full text]
  • New High‐Resolution Age Data from the Ediacaran–Cambrian Boundary Indicate Rapid, Ecologically Driven Onset of the Cambrian Explosion
    Received: 14 June 2018 | Revised: 6 October 2018 | Accepted: 19 October 2018 DOI: 10.1111/ter.12368 PAPER New high‐resolution age data from the Ediacaran–Cambrian boundary indicate rapid, ecologically driven onset of the Cambrian explosion Ulf Linnemann1 | Maria Ovtcharova2 | Urs Schaltegger2 | Andreas Gärtner1 | Michael Hautmann3 | Gerd Geyer4 | Patricia Vickers-Rich5,6,7 | Tom Rich6 | Birgit Plessen8 | Mandy Hofmann1 | Johannes Zieger1 | Rita Krause1 | Les Kriesfeld7 | Jeff Smith7 1Senckenberg Collections of Natural History Dresden, Museum of Mineralogy Abstract and Geology, Dresden, Germany The replacement of the late Precambrian Ediacaran biota by morphologically disparate 2Département des Sciences de la Terre, animals at the beginning of the Phanerozoic was a key event in the history of life on University of Geneva, Genève, Switzerland ‐ 3Paläontologisches Institut und Museum, Earth, the mechanisms and the time scales of which are not entirely understood. A Zürich, Switzerland composite section in Namibia providing biostratigraphic and chemostratigraphic data 4 Bayerische Julius-Maximilians-Universität, bracketed by radiometric dating constrains the Ediacaran–Cambrian boundary to Lehrstuhl für Geodynamik und Geomaterialforschung, Würzburg, Germany 538.6–538.8 Ma, more than 2 Ma younger than previously assumed. The U–Pb‐CA‐ID 5Department of Chemistry and TIMS zircon ages demonstrate an ultrashort time frame for the LAD of the Ediacaran Biotechnology, Swinburne University of Technology, Melbourne (Hawthorne), biota to the FAD of a complex, burrowing Phanerozoic biota represented by trace fos- Victoria, Australia sils to a 410 ka time window of 538.99 ± 0.21 Ma to 538.58 ± 0.19 Ma. The extre- 6 Museums Victoria, Melbourne, Victoria, mely short duration of the faunal transition from Ediacaran to Cambrian biota within Australia less than 410 ka supports models of ecological cascades that followed the evolution- 7School of Earth, Atmosphere and Environment, Monash University, ary breakthrough of increased mobility at the beginning of the Phanerozoic.
    [Show full text]
  • New Ediacara Fossils Preserved in Marine Limestone and Their Ecological Implications
    OPEN New Ediacara fossils preserved in SUBJECT AREAS: marine limestone and their ecological PALAEONTOLOGY GEOLOGY implications Zhe Chen1, Chuanming Zhou1, Shuhai Xiao2, Wei Wang1, Chengguo Guan1, Hong Hua3 & Xunlai Yuan1 Received 22 November 2013 1LPS and LESP, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China, Accepted 2Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA, 3State Key Laboratory 7 February 2014 of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China. Published 25 February 2014 Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preserved in sandstones and Correspondence and siltstones. Here we report several iconic Ediacara fossils and an annulated tubular fossil (reconstructed as an requests for materials erect epibenthic organism with uniserial arranged modular units), from marine limestone of the 551– should be addressed to 541 Ma Dengying Formation in South China. These fossils significantly expand the ecological ranges of Z.C. (zhechen@ several key Ediacara taxa and support that they are marine organisms rather than terrestrial lichens or nigpas.ac.cn) or microbial colonies. Their close association with abundant bilaterian burrows also indicates that they could tolerate and may have survived moderate levels of bioturbation. S.H.X. ([email protected]) he Ediacara biota, exemplified by fossils preserved in the Ediacara Member of South Australia, provides key information about the origin, diversification, and disappearance of a distinct group of soft-bodied, mac- T roscopic organisms on the eve of the Cambrian diversification of marine animals1–3.
    [Show full text]
  • NEW FAIJNAL DISCOVERIES in the LATE NEOPROTEROZOIC of SOUTH ~~USTRALIA Ai'j"D THEIR POTENTIAL SIGNIFICANCE in the EMERGING CHRONOMETRY of the EDIACARAN
    197 NEW FAIJNAL DISCOVERIES IN THE LATE NEOPROTEROZOIC OF SOUTH ~~USTRALIA Ai'J"D THEIR POTENTIAL SIGNIFICANCE IN THE EMERGING CHRONOMETRY OF THE EDIACARAN. JENKlNS*, Richard F.J. and NEDIN, Christopher, Dept. of Geology and Geophysics, The University of Adelaide, 4~delaide, SA, 5005, AUSTRALIA. Investigation of the late Neoproteozoic Rawnsley Quartzite in the western Hinders Ranges has disclosed four additional, hitherto unsuspected, erosive sequence tract boundaries. The base of the shorefacelintertidal 'member l' of the Rawnsley QUaltzite overlies the fluviatile and paralic Bonney Sandstone at an erosive surface which locally exhibits low angle (c. 2°) discordance. Further erosive surfaces separate member 1 from the transgressive-regressive cycles of members '2' and '3' as well as the well known Ediacara Member, which contains the type Ediacara assemblage of soft-bodied metazoan remains. Another downcutting surface occurs at the top of this member and a further one at the local base of the Cambrian. The sequence boundaries within the Rawnsley Quartzite locally erode down c. 10 - 30m through underlying strata, but the surface below 'member 3' forms deep channels with up to c. 175m of relief. Small discoidal 'fossil' remains occur rarely in the Bonney Sandstone and earlier evidence of metazoans extends down to the upper Wonoka Formation. Careful search of 'member l' of the Rawnsley Quartzite has so far revealed only net-like imprints assumed to be moulds of cyanobacterial mats. 'Member 2' includes a diverse fauna with Rangea- and Emietta-like forms, a Pteridinium sp., Kullingia, Hiemalora, rare Tribrachidium, rare Dickinsonia (2 species), common simple trace fossils and 'Chondrites'.
    [Show full text]
  • The Influence of Environmental Setting on the Community Ecology of Ediacaran Organisms
    bioRxiv preprint doi: https://doi.org/10.1101/861906; this version posted December 2, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 1 The influence of environmental setting on the community ecology of Ediacaran organisms 2 3 Emily G. Mitchell1, Nikolai Bobkov2,3, Natalia Bykova2,4, Alavya Dhungana,5, Anton 4 Kolesnikov2,6, 7, Ian R. P. Hogarth8,9 Alexander G. Liu10, Tom M.R. Mustill10,11, Nikita 5 Sozonov2,3, Shuhai Xiao4 and Dmitriy V. Grazhdankin2,3 . 6 7 [email protected] 8 9 1Department of Zoology, University of Cambridge, UK. 10 2Institute of Petroleum Geology and Geophysics, Novosibirsk, Russian Federation. 11 3Novosibirsk State University, Russian Federation. 12 4Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, United States. 13 5 Department of Earth Sciences, Durham University, UK. 14 6Geological Institute, Russian Academy of Sciences, Moscow, Russian Federation. 15 7Department of Geography, Moscow Pedagogical State University, Moscow, Russian 16 Federation. 17 8Department of Chemical Engineering, University of Cambridge, UK. 18 9Current address: University College London, UCL Institute for Innovation and Public 19 Purpose, UK. 20 10Department of Earth Sciences, University of Cambridge, UK. 21 11Current address: Gripping Films, St. John's Church Road, London, England, E9 6EJ. 22 23 24 1 bioRxiv preprint doi: https://doi.org/10.1101/861906; this version posted December 2, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
    [Show full text]
  • Taphonomy of the Ediacaran Fossil Pteridinium Simplex Preserved Three
    Taphonomy of the Ediacaran Fossil Pteridinium Simplex Preserved Three- Dimensionally in Mass Flow Deposits, Nama Group, Namibia Author(s): Mike Meyer , David Elliott , James D. Schiffbauer , Michael Hall , Karl H. Hoffman , Gabi Schneider , Patricia Vickers-Rich , and Shuhai Xiao Source: Journal of Paleontology, 88(2):240-252. 2014. Published By: The Paleontological Society DOI: http://dx.doi.org/10.1666/13-047 URL: http://www.bioone.org/doi/full/10.1666/13-047 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Journal of Paleontology, 88(2), 2014, p. 240–252 Copyright Ó 2014, The Paleontological Society 0022-3360/14/0088-0240$03.00 DOI: 10.1666/13-047 TAPHONOMY OF THE EDIACARAN FOSSIL PTERIDINIUM SIMPLEX PRESERVED THREE-DIMENSIONALLY IN MASS FLOW DEPOSITS, NAMA GROUP, NAMIBIA MIKE MEYER,1,5 DAVID ELLIOTT,2 JAMES D. SCHIFFBAUER,3 MICHAEL HALL,2 KARL H.
    [Show full text]
  • New Evidence on the Taphonomic Context of the Ediacaran Pteridinium
    New evidence on the taphonomic context of the Ediacaran Pteridinium DAVID A. ELLIOTT, PATRICIA VICKERS−RICH, PETER TRUSLER, and MIKE HALL Elliott, D.A., Vickers−Rich, P., Trusler, P., and Hall, M. 2011. New evidence on the taphonomic context of the Ediacaran Pteridinium. Acta Palaeontologica Polonica 56 (3): 641–650. New material collected from the Kliphoek Member of the Nama Group (Kuibis Subgroup, Dabis Formation) on Farm Aar, southern Namibia, offers insights concerning the morphology of the Ediacaran organism Pteridinium. Pteridinium fossils previously described as being preserved in situ have been discovered in association with scour−and−fill structures indicative of transport. Additionally, two Pteridinium fossils have been found within sedimentary dish structures in the Kliphoek Member. A form of organic surface with a discrete membrane−like habit has also been recovered from Farm Aar, and specimens exist with both Pteridinium and membrane−like structures superimposed. The association between Pteridinium fossils and membrane−like structures suggests several possibilities. Pteridinium individuals may have been transported before burial along with fragments of microbial mat; alternately they may have been enclosed by an external membranous structure during life. Key words: Pteridinium, Petalonamae, Vendobionta, taphonomy, palaeoecology, Kliphoek Member, Nama Group, Ediacaran. David A. Elliott [[email protected]], Patricia Vickers−Rich [[email protected]], Peter Trusler [pe− [email protected]], and Mike Hall [[email protected]], School of Geosciences, Monash University, Vic− toria, Australia 3800. Received 27 May 2010, accepted 21 October 2010, available online 22 October 2010. Introduction up−section. The Kliphoek Member represents the sandstone phase of the second of these cycles (Gresse and Germs 1993; Members of the genus Pteridinium were first described as Saylor et al.
    [Show full text]
  • The Palaeontology Newsletter
    The Palaeontology Newsletter Contents100 Editorial 2 Association Business 3 Annual Meeting 2019 3 Awards and Prizes AGM 2018 12 PalAss YouTube Ambassador sought 24 Association Meetings 25 News 30 From our correspondents A Palaeontologist Abroad 40 Behind the Scenes: Yorkshire Museum 44 She married a dinosaur 47 Spotlight on Diversity 52 Future meetings of other bodies 55 Meeting Reports 62 Obituary: Ralph E. Chapman 67 Grant Reports 72 Book Reviews 104 Palaeontology vol. 62 parts 1 & 2 108–109 Papers in Palaeontology vol. 5 part 1 110 Reminder: The deadline for copy for Issue no. 101 is 3rd June 2019. On the Web: <http://www.palass.org/> ISSN: 0954-9900 Newsletter 100 2 Editorial This 100th issue continues to put the “new” in Newsletter. Jo Hellawell writes about our new President Charles Wellman, and new Publicity Officer Susannah Lydon gives us her first news column. New award winners are announced, including the first ever PalAss Exceptional Lecturer (Stephan Lautenschlager). (Get your bids for Stephan’s services in now; check out pages 34 and 107.) There are also adverts – courtesy of Lucy McCobb – looking for the face of the Association’s new YouTube channel as well as a call for postgraduate volunteers to join the Association’s outreach efforts. But of course palaeontology would not be the same without the old. Behind the Scenes at the Museum returns with Sarah King’s piece on The Yorkshire Museum (York, UK). Norman MacLeod provides a comprehensive obituary of Ralph Chapman, and this issue’s palaeontologists abroad (Rebecca Bennion, Nicolás Campione and Paige dePolo) give their accounts of life in Belgium, Australia and the UK, respectively.
    [Show full text]
  • CAMBRIAN SURVIVOR AMONG SMALL CARBONACEOUS FOSSILS (SCFS) by BEN J
    [Palaeontology, Vol. 63, Part 5, 2020, pp. 733–752] COCHLEATINA: AN ENIGMATIC EDIACARAN– CAMBRIAN SURVIVOR AMONG SMALL CARBONACEOUS FOSSILS (SCFS) by BEN J. SLATER1 ,THOMASH.P.HARVEY2, ANDREY BEKKER3 and NICHOLAS J. BUTTERFIELD4 1Department of Earth Sciences, Palaeobiology, Uppsala University, Villav€agen 16, Uppsala 752 36, Sweden; [email protected], [email protected] 2School of Geography, Geology & the Environment, University of Leicester, University Rd, Leicester LE1 7RH, UK 3Department of Earth & Planetary Sciences, UC Riverside, 900 University Av., Riverside, CA 92521, USA 4Department of Earth Sciences, University of Cambridge, Downing St, Cambridge CB2 3EQ, UK Typescript received 26 November 2019; accepted in revised form 6 March 2020 Abstract: Conspicuously few body-fossil taxa are known descriptions for Cochleatina and C. canilovica, and critically to span the Ediacaran–Cambrian boundary, a pattern usually evaluate previous biological interpretations, drawing compar- taken to signal either a terminal Proterozoic mass extinction, isons with metazoan, algal and protistan analogues. We or taphonomic failure. We draw attention to the emerging reject hypotheses supporting Cochleatina as a metazoan record of small carbonaceous fossils (SCFs), which exhibit mouthpart, and suggest new grounds for viewing Cochleatina continuous preservation spanning this critical interval. Here as a potential multicomponent predator that trapped protists we focus on the enigmatic SCF Cochleatina, a morphologi- among microbial mats. Most occurrences are from Baltica, cally complex coil-shaped problematicum that ranges across but we synthesize sporadic reports of Cochleatina from other the Ediacaran–Cambrian divide, and is potentially among palaeocontinents, pointing to its global distribution during the oldest fossil occurrences of metazoans. We report new the latest ~10 myr of the Ediacaran and majority of the ear- material of Cochleatina canilovica from the Ediacaran of liest Cambrian Fortunian Stage.
    [Show full text]
  • A Placozoan Affinity for Dickinsonia and the Evolution of Late Proterozoic Metazoan Feeding Modes
    EVOLUTION & DEVELOPMENT 12:2, 201–209 (2010) DOI: 10.1111/j.1525-142X.2010.00404.x A placozoan affinity for Dickinsonia and the evolution of late Proterozoic metazoan feeding modes Erik A. Sperlingà and Jakob Vinther Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA ÃAuthor for correspondence (email: [email protected]) SUMMARY Dickinsonia is one of the most recognizable fungal, or sponge affinity, while the feeding mode, external forms in the Ediacaran fauna, but its phylogenetic position has digestion with a ventral sole, rules out placement within any been contentious, and it has been placed in almost every sponge or eumetazoan lineage. The only organisms that both kingdom of life. Here, it is hypothesized that the affinities of move and feed in this manner are placozoans. Recent Dickinsonia lie with the Placozoa (Metazoa), an understudied molecular phylogenetic studies have demonstrated that phylum that is widespread in tropical seas worldwide. Modern placozoans lie above sponges but below Eumetazoa. We placozoans show obvious differences in size and axial hypothesize that Dickinsonia and other externally digesting organization compared with Dickinsonia, but these Ediacaran forms are either stem-placozoans, or a series of differences can be accounted for by the stem-group/crown- extinct lineages above sponges and below eumetazoans on group distinction. The affinity with placozoans is evidenced the metazoan tree. We discuss the potential evolutionary primarily by the unique feeding mode of Dickinsonia, which is transitions between the main metazoan feeding modes in demonstrated by a series of feeding traces. These traces the context of the emerging molecular phylogeny, and sug- indicate that Dickinsonia moved over the Ediacaran gest that aspects of the sponge and placozoan feeding matgrounds, and digested the mat using its entire lower strategies are relicts of nonuniformitarian Proterozoic ocean sole.
    [Show full text]