Biotic Changes Through the Ediacaran-Cambrian Transition: Insights from Arctic Norway

Total Page：16

File Type：pdf, Size：1020Kb

Biotic Changes Through the Ediacaran-Cambrian Transition: Insights from Arctic Norway

UC SANTA BARBARA Department of Earth Science Zoom ID:no password 923 8742 needed 1224 Earth Science Colloquium more info: geol.ucsb.edu/news/calendar THURSDAY April 23rd., 2020 • 2:00 PM Biotic changes through the Ediacaran-Cambrian transition: insights from Arctic Norway Heda Agić Department of Earth Science, UC Santa Barbara The first abundant macroscopic organisms in the fossil record make their appearance at the end of the Neoproterozoic Era. These are collectively termed Ediacara-type organisms, and mark the diversification of multicellular life. Digermulen Peninsula, part of the northernmost Norwegian mainland, contains a nearly continuous sequence of shales, siltstones, and sandstones deposited from the Cryogenian to the Ordovician. Integrated palaeontological and sedimentological data from such a rare locality recording this interval, allows us to investigate the sequential biotic changes during the Ediacaran-Cambrian transition on the Baltica palaeocontinent. Early Ediacaran strata on Digermulen contain large organic-walled microfossils of single-celled eukaryotes (acanthomorphic acritrachs) and unusual tiny remains of multicellular tissue. Above the Mortensnes diamitite correlated with the Gaskiers glaciation, the first macroscopic Ediacara-type impressions are abundant, including discoidal and rangeomorph fossils and the possible bilaterian Dickinsonia. A striking decline in the diversity of soft- bodied ediacarans corresponds to increasing diversity of trace fossils showing expansion behavioural complexity through bioturbation. Depauperate diversity marks the latest Ediacaran and the earliest Cambrian, and the ediacarans are replaced by organically- preserved putative annelid worm Sabellidites and an increasing diversity of skeletal organisms like trilobites. In this talk I’ll present results from several field seasons, focusing on (1) the cryptic origin of multicellularity before the appearance of macroscopic fossils, (2) evolution of microscopic eukaryotes through the Ediacaran glaciation and the appearance of animals, and (3) how the Digermulen macrofossil assemblage fits into our understanding of the Ediacaran evolutionary biotas and their demise during the late Ediacaran increase in bioturbation..

Copy Link

Recommended publications

Geobiological Events in the Ediacaran Period
Geobiological Events in the Ediacaran Period Shuhai Xiao Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA NSF; NASA; PRF; NSFC; Virginia Tech Geobiology Group; CAS; UNLV; UCR; ASU; UMD; Amherst; Subcommission of Neoproterozoic Stratigraphy; 1 Goals To review biological (e.g., acanthomorphic acritarchs; animals; rangeomorphs; biomineralizing animals), chemical (e.g., carbon and sulfur isotopes, oxygenation of deep oceans), and climatic (e.g., glaciations) events in the Ediacaran Period; To discuss integration and future directions in Ediacaran geobiology; 2 Knoll and Walter, 1992 • Acanthomorphic acritarchs in early and Ediacara fauna in late Ediacaran Period; • Strong carbon isotope variations; • Varanger-Laplandian glaciation; • What has happened since 1992? 3 Age Constraints: South China (538.2±1.5 Ma) 541 Ma Cambrian Dengying Ediacaran Sinian 551.1±0.7 Ma Doushantuo 632.5±0.5 Ma 635 Ma 635.2±0.6 Ma Nantuo (Tillite) 636 ± 5Ma Cryogenian Nanhuan 654 ± 4Ma Datangpo 663±4 Ma Neoproterozoic Neoproterozoic Jiangkou Group Banxi Group 725±10 Ma Tonian Qingbaikouan 1000 Ma • South China radiometric ages: Condon et al., 2005; Hoffmann et al., 2004; Zhou et al., 2004; Bowring et al., 2007; S. Zhang et al., 2008; Q. Zhang et al., 2008; • Additional ages from Nama Group (Namibia), Conception Group (Newfoundland), and Vendian (White Sea); 4 The Ediacaran Period Ediacara fossils Cambrian 545 Ma Nama assemblage 555 Ma White Sea assemblage 565 Ma Avalon assemblage 575 Ma 585 Ma Doushantuo biota 595 Ma 605 Ma Ediacaran Period 615 Ma
[Show full text]
The Ediacaran–Cambrian Transition: the Emerging Record from Small Carbonaceous Fossils (Scfs)
38 The Ediacaran–Cambrian transition: the emerging record from Small Carbonaceous Fossils (SCFs) Ben J. Slater1, Thomas H.P. Harvey2, Romain Guilbaud3, Sebastian Willman1, Graham E. Budd1, Nicholas J. Butterfield4. 1Department of Earth Sciences (Palaeobiology), Uppsala University, Villavägen 16, SE-75236 Uppsala, Sweden ([email protected]) 2School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK 3Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK. 4Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK Abstract.––The most profound change in the fossil record is centered on the Ediacaran–Cambrian transition. Sediments deposited near to this boundary record the first complex trace fossils, the first animal biomineralizers and the earliest fossils of the major animal groups that came to define the subsequent Phanerozoic fossil record. Here we discuss how the emerging record of small carbonaceous fossils (SCFs) is shedding new light on unmineralized aspects of the biota from this critical evolutionary transition. The new SCFs record complements currently established records from trace fossils and biomineralized shelly-remains in reconstructing the broader scale macroevolutionary patterns of this transition, but via an entirely different taphonomic window. SCFs extend the record of multiple major animal groups, improve our picture of protistan diversity from this interval, and reveal new data on elements of the biota that span the Ediacaran–Cambrian boundary. Key words: small carbonaceous fossils; bilateria; Burgess Shale-type preservation; Ediacaran; Terreneuvian. The dramatic changes in the fossil record across subsequent Cambrian radiation (Butterfield, the Ediacaran–Cambrian transition seemingly 2003; Slater et al., 2018a).
[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]
Rangeomorph Classification Schemes and Intra-Specific Variation: Are All
Downloaded from http://sp.lyellcollection.org/ by guest on September 23, 2021 Rangeomorph classification schemes and intra-specific variation: are all characters created equal? CHARLOTTE G. KENCHINGTON1,2* & PHILIP R. WILBY3 1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK 2Present address: Department of Earth Sciences, Memorial University of Newfoundland, Prince Philip Drive, St John’s, NL, A1B 3X5, Canada 3British Geological Survey, Environmental Science Centre, Nicker Hill, Keyworth, Nottingham NG12 5GG, UK *Correspondence: [email protected] Abstract: Rangeomorphs from the Ediacaran of Avalonia are among the oldest known complex macrofossils and our understanding of their ecology, ontogeny and phylogenetic relationships relies on accurate and consistent classification. There are a number of disparate classification schemes for this group, which dominantly rely on a combination of their branching characters and shape metrics. Using multivariate statistical analyses and the diverse stemmed, multifoliate rangeomorphs in Charnwood Forest (UK), we assess the taxonomic usefulness of the suite of char- acters currently in use. These techniques allow us to successfully discriminate taxonomic groupings without a priori assumptions or weighting of characters and to document a hitherto unrecognized level of variation within single taxonomic groups. Variation within the currently defined genus Pri- mocandelabrum is too great to be realistically assigned to different species and may instead reflect primary character diversity, ontogenetic changes in character state or ecophenotypic variability. Its recognition cautions against generic-level diagnoses based on single differences in character state and will be crucial in understanding the mode of growth of these enigmatic organisms. Supplementary material: Data tables, definition of the characters used in the analyses, and detailed descriptions and breakdowns of methods and results are available at https://doi.org/10.
[Show full text]
Subglacial Meltwater Supported Aerobic Marine Habitats During Snowball Earth
Subglacial meltwater supported aerobic marine habitats during Snowball Earth Maxwell A. Lechtea,b,1, Malcolm W. Wallacea, Ashleigh van Smeerdijk Hooda, Weiqiang Lic, Ganqing Jiangd, Galen P. Halversonb, Dan Asaele, Stephanie L. McColla, and Noah J. Planavskye aSchool of Earth Sciences, University of Melbourne, Parkville, VIC 3010, Australia; bDepartment of Earth and Planetary Science, McGill University, Montréal, QC, Canada H3A 0E8; cState Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 210093 Nanjing, China; dDepartment of Geoscience, University of Nevada, Las Vegas, NV 89154; and eDepartment of Geology and Geophysics, Yale University, New Haven, CT 06511 Edited by Paul F. Hoffman, University of Victoria, Victoria, BC, Canada, and approved November 3, 2019 (received for review May 28, 2019) The Earth’s most severe ice ages interrupted a crucial interval in Cryogenian ice age. These marine chemical sediments are unique eukaryotic evolution with widespread ice coverage during the geochemical archives of synglacial ocean chemistry. To develop Cryogenian Period (720 to 635 Ma). Aerobic eukaryotes must have sur- a global picture of seawater redox state during extreme glaci- vived the “Snowball Earth” glaciations, requiring the persistence of ation, we studied 9 IF-bearing Sturtian glacial successions across 3 oxygenated marine habitats, yet evidence for these environments paleocontinents (Fig. 1): Congo (Chuos Formation, Namibia), is lacking. We examine iron formations within globally distributed Australia (Yudnamutana Subgroup), and Laurentia (Kingston Cryogenian glacial successions to reconstruct the redox state of the Peak Formation, United States). These IFs were selected for synglacial oceans. Iron isotope ratios and cerium anomalies from a analysis because they are well-preserved, and their depositional range of glaciomarine environments reveal pervasive anoxia in the environment can be reliably constrained.
[Show full text]
Fossils, Feeding, and the Evolution of Complex Multicellularity
Fossils, Feeding, and the Evolution of Complex Multicellularity The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Knoll, Andrew H., and Daniel J.G. Lahr. 2016. "Fossils, feeding, and the evolution of complex multicellularity." In Multicellularity, Origins and Evolution, The Vienna Series in Theoretical Biology, eds. Karl J. Niklas and Stuart A. Newman. Cambridge, MA: MIT Press. Published Version https://mitpress.mit.edu/books/multicellularity Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:34390340 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#OAP Fossils, Feeding, and the Evolution of Complex Multicellularity Andrew H. Knoll and Daniel J. G. Lahr Andrew H. Knoll Department of Organismic and Evolutionary Biology, Harvard University Daniel J.G. Lahr Department of Zoology, Institute of Biosciences, University of São Paulo The evolution of complex multicellularity is commonly viewed as a series of genomic events with developmental consequences. It is surely that, but a focus on feeding encourages us to view it, as well, in terms of functional events with ecological consequences. And fossils remind us that these events are also historical, with environmental constraints and consequences. Several definitions of complex multicelluarity are possible; here we adopt to view that complex multicellular organisms are those with tissues or organs that permit bulk nutrient and gas transport, thereby circumventing the limitations of diffusion (Knoll, 2011).
[Show full text]
Annual Meeting 2011
The Palaeontological Association 55th Annual Meeting 17th–20th December 2011 Plymouth University PROGRAMME and ABSTRACTS Palaeontological Association 2 ANNUAL MEETING ANNUAL MEETING Palaeontological Association 1 The Palaeontological Association 55th Annual Meeting 17th–20th December 2011 School of Geography, Earth and Environmental Sciences, Plymouth University The programme and abstracts for the 55th Annual Meeting of the Palaeontological Association are outlined after the following summary of the meeting. Venue The meeting will take place on the campus of Plymouth University. Directions to the University and a campus map can be found at <http://www.plymouth.ac.uk/location>. The opening symposium and the main oral sessions will be held in the Sherwell Centre, located on North Hill, on the east side of campus. Accommodation Delegates need to make their own arrangements for accommodation. Plymouth has a large number of hotels, guesthouses and hostels at a variety of prices, most of which are within ~1km of the University campus (hotels with PL1 or PL4 postcodes are closest). More information on these can be found through the usual channels, and a useful starting point is the website <http://www.visitplymouth.co.uk/site/where-to-stay>. In addition, we have organised discount rates at the Jury’s Inn, Exeter Street, which is located ~500m from the conference venue. A maximum of 100 rooms have been reserved, and will be allocated on a first-come-first-served basis. Further information can be found on the Association’s website. Travel Transport into Plymouth can be achieved via a variety of means. Travel by train from London Paddington to Plymouth takes between three and four hours depending on the time of day and the number of stops.
[Show full text]
Rangeomorph Classification Schemes and Intra-Specific Variation: Are All
Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 Rangeomorph classification schemes and intra-specific variation: are all characters created equal? CHARLOTTE G. KENCHINGTON1,2* & PHILIP R. WILBY3 1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK 2Present address: Department of Earth Sciences, Memorial University of Newfoundland, Prince Philip Drive, St John’s, NL, A1B 3X5, Canada 3British Geological Survey, Environmental Science Centre, Nicker Hill, Keyworth, Nottingham NG12 5GG, UK *Correspondence: [email protected] Abstract: Rangeomorphs from the Ediacaran of Avalonia are among the oldest known complex macrofossils and our understanding of their ecology, ontogeny and phylogenetic relationships relies on accurate and consistent classification. There are a number of disparate classification schemes for this group, which dominantly rely on a combination of their branching characters and shape metrics. Using multivariate statistical analyses and the diverse stemmed, multifoliate rangeomorphs in Charnwood Forest (UK), we assess the taxonomic usefulness of the suite of char- acters currently in use. These techniques allow us to successfully discriminate taxonomic groupings without a priori assumptions or weighting of characters and to document a hitherto unrecognized level of variation within single taxonomic groups. Variation within the currently defined genus Pri- mocandelabrum is too great to be realistically assigned to different species and may instead reflect primary character diversity, ontogenetic changes in character state or ecophenotypic variability. Its recognition cautions against generic-level diagnoses based on single differences in character state and will be crucial in understanding the mode of growth of these enigmatic organisms. Supplementary material: Data tables, definition of the characters used in the analyses, and detailed descriptions and breakdowns of methods and results are available at https://doi.org/10.
[Show full text]
Ediacaran Life Close to Land: Coastal and Shoreface Habitats of the Ediacaran Macrobiota, the Central Flinders Ranges, South Australia
Journal of Sedimentary Research, 2020, v. 90, 1463–1499 Research Article DOI: 10.2110/jsr.2020.029 EDIACARAN LIFE CLOSE TO LAND: COASTAL AND SHOREFACE HABITATS OF THE EDIACARAN MACROBIOTA, THE CENTRAL FLINDERS RANGES, SOUTH AUSTRALIA 1 2 2 1 WILLIAM J. MCMAHON,* ALEXANDER G. LIU, BENJAMIN H. TINDAL, AND MAARTEN G. KLEINHANS 1Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB, Utrecht, The Netherlands 2Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K. [email protected] ABSTRACT: The Rawnsley Quartzite of South Australia hosts some of the world’s most diverse Ediacaran macrofossil assemblages, with many of the constituent taxa interpreted as early representatives of metazoan clades. Globally, a link has been recognized between the taxonomic composition of individual Ediacaran bedding-plane assemblages and speciﬁc sedimentary facies. Thorough characterization of fossil-bearing facies is thus of fundamental importance for reconstructing the precise environments and ecosystems in which early animals thrived and radiated, and distinguishing between environmental and evolutionary controls on taxon distribution. This study reﬁnes the paleoenvironmental interpretations of the Rawnsley Quartzite (Ediacara Member and upper Rawnsley Quartzite). Our analysis suggests that previously inferred water depths for fossil-bearing facies are overestimations. In the central regions of the outcrop belt, rather than shelf and submarine canyon environments below maximum (storm-weather) wave base,
[Show full text]
International Conference on Ediacaran and Cambrian Sciences Joint Meeting of Ediacaran and Cambrian Subcommissions
First circular June 10 2017 International Conference on Ediacaran and Cambrian Sciences Joint Meeting of Ediacaran and Cambrian Subcommissions 11-21 August 2018, Xian, China Xian, the eternal city, records the great changes of the Chinese nation just like a living history book. Called Chang'an in ancient times, Xian is one of the birthplaces of the ancient civilization in the Yellow River Basin area of the country. During Xian's 3,100 year development, 13 dynasties such as Western Zhou (11th century BC - 771 BC), Qin (221 BC - 206 BC)…. Western Han (206 BC - 24 AD) ... Three-day topic sessions will focus on Neoproterozoic-Cambrian life and Sponsors environments. Pre- and post-conference field excursions Shaanxi Key Laboratory of Early Life and will be arranged and the cost will be Environments provided in subsequent circulars. State Key Laboratory of Continental Dynamics One-day city tour will be organized. Organizing committee Department of Geology Yaoping Cai, Jian Han, Hong Hua, Kangjun Huang, Northwest University Jianni Liu, Xingliang Zhang (chair), Zhifei Zhang Shaanxi Paleontological Society Secretaries Dongjing Fu, Wei Liu State Key Laboratory of ([email protected]), ([email protected]) Palaeontology and Stratigraphy (Nanjing) Scientific Committee Per Alhberg, Loren Babcock, Dima Grazhdankin, Marc Laflamme, Guoxiang Li, Pengju Liu, Shanchi Peng, Degan Shu (chair), Shuhai Xiao, Xunlai Yuan, Chuanming Zhou, Maoyan Zhu. Precambrian-Cambrian transition in the southern margin of North China plate in the northern margin of South China plate Field excursions Pre-conference field excursion 11-12 August 20182016 Precambrian-Cambrian transition in the southern margin of North China This two- or three-day pre- conference field trip will depart from and come back to Xian.
[Show full text]
Ediacaran Extinction and Cambrian Explosion
Opinion Ediacaran Extinction and Cambrian Explosion 1, 2 3 4 Simon A.F. Darroch, * Emily F. Smith, Marc Laflamme, and Douglas H. Erwin The Ediacaran–Cambrian (E–C) transition marks the most important geobio- Highlights logical revolution of the past billion years, including the Earth’s first crisis of We provide evidence for a two-phased biotic turnover event during the macroscopic eukaryotic life, and its most spectacular evolutionary diversifica- Ediacaran–Cambrian transition (about tion. Here, we describe competing models for late Ediacaran extinction, 550–539 Ma), which both comprises the Earth’s first major biotic crisis of summarize evidence for these models, and outline key questions which will macroscopic eukaryotic life (the disap- drive research on this interval. We argue that the paleontological data suggest pearance of the enigmatic ‘Ediacara – – two pulses of extinction one at the White Sea Nama transition, which ushers biota’) and immediately precedes the Cambrian explosion. in a recognizably metazoan fauna (the ‘Wormworld’), and a second pulse at the – E C boundary itself. We argue that this latest Ediacaran fauna has more in Wesummarizetwocompetingmodelsfor – common with the Cambrian than the earlier Ediacaran, and thus may represent the turnover pulses an abiotically driven model(catastrophe)analogoustothe‘Big the earliest phase of the Cambrian Explosion. 5’ Phanerozoic mass extinction events, and a biotically driven model (biotic repla- Evolutionary and Geobiological Revolution in the Ediacaran cement) suggesting that the evolution of The late Neoproterozoic Ediacara biota (about 570–539? Ma) are an enigmatic group of soft- bilaterian metazoans and ecosystem engineering were responsible. bodied organisms that represent the first radiation of large, structurally complex multicellular eukaryotes.
[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]