1
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Retallack GJ. Damaged Dickinsonia specimens provide clues to Ediacaran vendobiont biology. PLoS One 2022; 17:e0269638. [PMID: 35709144 PMCID: PMC9202952 DOI: 10.1371/journal.pone.0269638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 05/19/2022] [Indexed: 12/14/2022] Open
Abstract
Recently reported specimens of the enigmatic Ediacaran fossil Dickinsonia from Russia show damage and repair that provides evidence of how they grew, and of their biological affinities. Marginal and terminal areas of wilting deformation are necrotic zones separating regenerated growth, sometimes on two divergent axes, rather than a single axis. Necrotic zones of damage to Dickinsonia are not a thick scar or callus, like a wound or amputation. Nor are they smooth transitions to a regenerated tail or arm. The wilted necrotic zone is most like damage by freezing, salt, or sunburn of leaves and lichens, compatible with evidence of terrestrial habitat from associated frigid and gypsic paleosols. Dickinsonia did not regrow by postembryonic addition of modules from a subterminal or patterned growth zone as in earthworms, myriapods, trilobites, crustaceans, and lizards. Rather Dickinsonia postembryonic regrowth from sublethal damage was from microscopic apical and lateral meristems, as in plants and lichens. Considered as fungal, Dickinsonia, and perhaps others of Class Vendobionta, were more likely Glomeromycota or Mucoromycotina, rather than Ascomycota or Basidiomycota.
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Affiliation(s)
- Gregory J. Retallack
- Department of Earth Sciences, University of Oregon, Eugene, Oregon, United States of America
- * E-mail:
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2
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Eden R, Manica A, Mitchell EG. Metacommunity analyses show an increase in ecological specialisation throughout the Ediacaran period. PLoS Biol 2022; 20:e3001289. [PMID: 35580078 PMCID: PMC9113585 DOI: 10.1371/journal.pbio.3001289] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 03/29/2022] [Indexed: 11/18/2022] Open
Abstract
The first animals appear during the late Ediacaran (572 to 541 Ma); an initial diversity increase was followed reduction in diversity, often interpreted as catastrophic mass extinction. We investigate Ediacaran ecosystem structure changes over this time period using the “Elements of Metacommunity Structure” framework to assess whether this diversity reduction in the Nama was likely caused by an external mass extinction, or internal metacommunity restructuring. The oldest metacommunity was characterised by taxa with wide environmental tolerances, and limited specialisation or intertaxa associations. Structuring increased in the second oldest metacommunity, with groups of taxa sharing synchronous responses to environmental gradients, aggregating into distinct communities. This pattern strengthened in the youngest metacommunity, with communities showing strong environmental segregation and depth structure. Thus, metacommunity structure increased in complexity, with increased specialisation and resulting in competitive exclusion, not a catastrophic environmental disaster, leading to diversity loss in the terminal Ediacaran. These results reveal that the complex eco-evolutionary dynamics associated with Cambrian diversification were established in the Ediacaran. This study shows that the eco-evolutionary dynamics of metazoan diversification known from the Cambrian Period started earlier in the Ediacaran Period with the Avalon assemblage and increased in complexity towards the Phanerozoic as new anatomical innovations appeared, culminating in the “Cambrian Explosion."
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Affiliation(s)
- Rebecca Eden
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Andrea Manica
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Emily G. Mitchell
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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3
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Abstract
AbstractAnimals, fungi, and algae with complex multicellular bodies all evolved independently from unicellular ancestors. The early history of these major eukaryotic multicellular clades, if not their origins, co-occur with an extreme phase of global glaciations known as the Snowball Earth. Here, I propose that the long-term loss of low-viscosity environments due to several rounds global glaciation drove the multiple origins of complex multicellularity in eukaryotes and the subsequent radiation of complex multicellular groups into previously unoccupied niches. In this scenario, life adapts to Snowball Earth oceans by evolving large size and faster speeds through multicellularity, which acts to compensate for high-viscosity seawater and achieve fluid flow at sufficient levels to satisfy metabolic needs. Warm, low-viscosity seawater returned with the melting of the Snowball glaciers, and with it, by virtue of large and fast multicellular bodies, new ways of life were unveiled.
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4
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Antell GT, Saupe EE. Bottom-up controls, ecological revolutions and diversification in the oceans through time. Curr Biol 2021; 31:R1237-R1251. [PMID: 34637737 DOI: 10.1016/j.cub.2021.08.069] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Animals originated in the oceans and evolved there for hundreds of millions of years before adapting to terrestrial environments. Today, oceans cover more than two-thirds of Earth and generate as much primary production as land. The path from the first macrobiota to modern marine biodiversity involved parallel increases in terrestrial nutrient input, marine primary production, species' abundance, metabolic rates, ecotypic diversity and taxonomic diversity. Bottom-up theories of ecosystem cascades arrange these changes in a causal sequence. At the base of marine food webs, nutrient fluxes and atmosphere-ocean chemistry interact with phytoplankton to regulate production. First-order consumers (e.g., zooplankton) might propagate changes in quantity and quality of phytoplankton to changes in abundance and diversity of larger predators (e.g., nekton). However, many uncertainties remain about the mechanisms and effect size of bottom-up control, particularly in oceans across the entire history of animal life. Here, we review modern and fossil evidence for hypothesized bottom-up pathways, and we assess the ramifications of these processes for four key intervals in marine ecosystems: the Ediacaran-Cambrian (635-485 million years ago), the Ordovician (485-444 million years ago), the Devonian (419-359 million years ago) and the Mesozoic (252-66 million years ago). We advocate for a clear articulation of bottom-up hypotheses to better understand causal relationships and proposed effects, combined with additional ecological experiments, paleontological documentation, isotope geochemistry and geophysical reconstructions. How small-scale ecological change transitions into large-scale evolutionary change remains an outstanding question for empirical and theoretical research.
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Affiliation(s)
- Gawain T Antell
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK.
| | - Erin E Saupe
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
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5
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Cracknell K, García-Bellido DC, Gehling JG, Ankor MJ, Darroch SAF, Rahman IA. Pentaradial eukaryote suggests expansion of suspension feeding in White Sea-aged Ediacaran communities. Sci Rep 2021; 11:4121. [PMID: 33602958 PMCID: PMC7893023 DOI: 10.1038/s41598-021-83452-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 02/03/2021] [Indexed: 01/31/2023] Open
Abstract
Suspension feeding is a key ecological strategy in modern oceans that provides a link between pelagic and benthic systems. Establishing when suspension feeding first became widespread is thus a crucial research area in ecology and evolution, with implications for understanding the origins of the modern marine biosphere. Here, we use three-dimensional modelling and computational fluid dynamics to establish the feeding mode of the enigmatic Ediacaran pentaradial eukaryote Arkarua. Through comparisons with two Cambrian echinoderms, Cambraster and Stromatocystites, we show that flow patterns around Arkarua strongly support its interpretation as a passive suspension feeder. Arkarua is added to the growing number of Ediacaran benthic suspension feeders, suggesting that the energy link between pelagic and benthic ecosystems was likely expanding in the White Sea assemblage (~ 558-550 Ma). The advent of widespread suspension feeding could therefore have played an important role in the subsequent waves of ecological innovation and escalation that culminated with the Cambrian explosion.
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Affiliation(s)
- Kelsie Cracknell
- grid.5337.20000 0004 1936 7603School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ UK
| | - Diego C. García-Bellido
- grid.1010.00000 0004 1936 7304School of Biological Sciences, University of Adelaide, North Terrace Campus, Adelaide, South Australia 5005 Australia ,grid.437963.c0000 0001 1349 5098South Australian Museum, Adelaide, South Australia 5000 Australia
| | - James G. Gehling
- grid.437963.c0000 0001 1349 5098South Australian Museum, Adelaide, South Australia 5000 Australia
| | - Martin J. Ankor
- grid.1010.00000 0004 1936 7304Department of Earth Sciences and Sprigg Geobiology Centre, University of Adelaide, North Terrace Campus, Adelaide, South Australia 5005 Australia
| | - Simon A. F. Darroch
- grid.152326.10000 0001 2264 7217Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37235-1805 USA ,grid.462628.c0000 0001 2184 5457Senckenberg Museum of Natural History, 60325 Frankfurt, Germany
| | - Imran A. Rahman
- grid.440504.10000 0000 8693 4250Oxford University Museum of Natural History, Oxford, OX1 3PW UK
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6
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Gibson BM, Furbish DJ, Rahman IA, Schmeeckle MW, Laflamme M, Darroch SAF. Ancient life and moving fluids. Biol Rev Camb Philos Soc 2020; 96:129-152. [PMID: 32959981 PMCID: PMC7821342 DOI: 10.1111/brv.12649] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 08/21/2020] [Accepted: 08/25/2020] [Indexed: 11/27/2022]
Abstract
Over 3.7 billion years of Earth history, life has evolved complex adaptations to help navigate and interact with the fluid environment. Consequently, fluid dynamics has become a powerful tool for studying ancient fossils, providing insights into the palaeobiology and palaeoecology of extinct organisms from across the tree of life. In recent years, this approach has been extended to the Ediacara biota, an enigmatic assemblage of Neoproterozoic soft‐bodied organisms that represent the first major radiation of macroscopic eukaryotes. Reconstructing the ways in which Ediacaran organisms interacted with the fluids provides new insights into how these organisms fed, moved, and interacted within communities. Here, we provide an in‐depth review of fluid physics aimed at palaeobiologists, in which we dispel misconceptions related to the Reynolds number and associated flow conditions, and specify the governing equations of fluid dynamics. We then review recent advances in Ediacaran palaeobiology resulting from the application of computational fluid dynamics (CFD). We provide a worked example and account of best practice in CFD analyses of fossils, including the first large eddy simulation (LES) experiment performed on extinct organisms. Lastly, we identify key questions, barriers, and emerging techniques in fluid dynamics, which will not only allow us to understand the earliest animal ecosystems better, but will also help to develop new palaeobiological tools for studying ancient life.
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Affiliation(s)
- Brandt M Gibson
- Department of Earth and Environmental Sciences, Vanderbilt University, PMB 351805, 2301 Vanderbilt Place, Nashville, TN, 37235-1805, U.S.A
| | - David J Furbish
- Department of Earth and Environmental Sciences, Vanderbilt University, PMB 351805, 2301 Vanderbilt Place, Nashville, TN, 37235-1805, U.S.A
| | - Imran A Rahman
- Oxford University Museum of Natural History, Parks Road, Oxford, OX1 3PW, U.K
| | - Mark W Schmeeckle
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ, 85281, U.S.A
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Rd North, Mississauga, Ontario, L5L 1C6, Canada
| | - Simon A F Darroch
- Department of Earth and Environmental Sciences, Vanderbilt University, PMB 351805, 2301 Vanderbilt Place, Nashville, TN, 37235-1805, U.S.A
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7
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Mángano MG, Buatois LA. The rise and early evolution of animals: where do we stand from a trace-fossil perspective? Interface Focus 2020; 10:20190103. [PMID: 32642049 DOI: 10.1098/rsfs.2019.0103] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2020] [Indexed: 01/10/2023] Open
Abstract
The trace-fossil record provides a wealth of information to track the rise and early evolution of animals. It comprises the activity of both hard- and soft-bodied organisms, is continuous through the Ediacaran (635-539 Ma)- Cambrian (539-485 Ma) transition, yields insights into animal behaviour and their role as ecosystem engineers, and allows for a more refined characterization of palaeoenvironmental context. In order to unravel macroevolutionary signals from the trace-fossil record, a variety of approaches is available, including not only estimation of degree of bioturbation, but also analysis of ichnodiversity and ichnodisparity trajectories, and evaluation of the occupation of infaunal ecospace and styles of ecosystem engineering. Analysis of the trace-fossil record demonstrates the presence of motile benthic bilaterians in the Ediacaran, mostly feeding from biofilms. Although Ediacaran trace fossils are simple and emplaced at or immediately below the sediment surface, an increase in ichnofossil complexity, predation pressure, sediment disturbance and penetration depth is apparent during the terminal Ediacaran. Regardless of this increase, a dramatic rise in trace fossil diversity and disparity took place during the earliest Cambrian, underscoring that the novelty of the Fortunian (539-529 Ma) cannot be underestimated. The Fortunian still shows the persistence of an Ediacaran-style matground ecology, but is fundamentally characterized by the appearance of new trace-fossil architectural plans reflecting novel ways of interacting with the substrate. The appearance of Phanerozoic-style benthic ecosystems attests to an increased length and connectivity of the food web and improved efficiency in organic carbon transfer and nutrient recycling. A profound reorganization of the infaunal ecospace is recorded in both high-energy sand-dominated nearshore areas and low-energy mud-dominated offshore environments, during the early Cambrian, starting approximately during Cambrian Age 2 (529-521 Ma), but continuing during the rest of the early Cambrian. A model comprising four evolutionary phases is proposed to synthetize information from the Ediacaran-Cambrian trace-fossil record. The use of a rich ichnological toolbox; critical, systematic and comprehensive evaluation of the Ediacaran-Cambrian trace-fossil record; and high-resolution integration of the ichnological dataset and sedimentological information show that the advent of biogenic mixing was an important factor in fully marine environments at the dawn of the Phanerozoic.
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Affiliation(s)
- M Gabriela Mángano
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Luis A Buatois
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan, Canada S7N 5E2
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Mitchell EG, Harris S, Kenchington CG, Vixseboxse P, Roberts L, Clark C, Dennis A, Liu AG, Wilby PR. The importance of neutral over niche processes in structuring Ediacaran early animal communities. Ecol Lett 2019; 22:2028-2038. [PMID: 31515929 PMCID: PMC6899650 DOI: 10.1111/ele.13383] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/01/2019] [Accepted: 08/11/2019] [Indexed: 01/22/2023]
Abstract
The relative influence of niche vs. neutral processes in ecosystem dynamics is an on-going debate, but the extent to which they structured the earliest animal communities is unknown. Some of the oldest known metazoan-dominated paleocommunities occur in Ediacaran age (~ 565 million years old) strata in Newfoundland, Canada and Charnwood Forest, UK. These comprise large and diverse populations of sessile organisms that are amenable to spatial point process analyses, enabling inference of the most likely underlying niche or neutral processes governing community structure. We mapped seven Ediacaran paleocommunities using LiDAR, photogrammetry and a laser line probe. We found that neutral processes dominate these paleocommunities, with niche processes exerting limited influence, in contrast with the niche-dominated dynamics of modern marine ecosystems. The dominance of neutral processes suggests that early metazoan diversification may not have been driven by systematic adaptations to the local environment, but instead may have resulted from stochastic demographic differences.
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Affiliation(s)
- Emily G. Mitchell
- Department of Earth SciencesUniversity of CambridgeDowning StreetCambridgeCB2 3EQUK
| | - Simon Harris
- British Geological SurveyNicker HillKeyworth, NottinghamNG12 5GGUK
| | | | - Philip Vixseboxse
- School of Earth SciencesUniversity of BristolWills Memorial Building, Queens RoadBristolBS8 1RJUK
| | - Lucy Roberts
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUK
| | - Catherine Clark
- Department of Earth SciencesUniversity of CambridgeDowning StreetCambridgeCB2 3EQUK
| | - Alexandra Dennis
- Department of Earth SciencesUniversity of CambridgeDowning StreetCambridgeCB2 3EQUK
| | - Alexander G. Liu
- Department of Earth SciencesUniversity of CambridgeDowning StreetCambridgeCB2 3EQUK
| | - Philip R. Wilby
- British Geological SurveyNicker HillKeyworth, NottinghamNG12 5GGUK
- School of Geography, Geology & the EnvironmentUniversity of LeicesterUniversity RoadLeicesterLE1 7RHUK
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9
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Cribb AT, Kenchington CG, Koester B, Gibson BM, Boag TH, Racicot RA, Mocke H, Laflamme M, Darroch SAF. Increase in metazoan ecosystem engineering prior to the Ediacaran-Cambrian boundary in the Nama Group, Namibia. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190548. [PMID: 31598294 PMCID: PMC6774933 DOI: 10.1098/rsos.190548] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 08/23/2019] [Indexed: 05/20/2023]
Abstract
The disappearance of the soft-bodied Ediacara biota at the Ediacaran-Cambrian boundary potentially represents the earliest mass extinction of complex life, although the precise driver(s) of this extinction remain unresolved. The 'biotic replacement' model proposes that an evolutionary radiation of metazoan ecosystem engineers in the latest Ediacaran profoundly altered marine palaeoenvironments, resulting in the extinction of Ediacara biota and setting the stage for the subsequent Cambrian Explosion. However, metazoan ecosystem engineering across the Ediacaran-Cambrian transition has yet to be quantified. Here, we test this key tenet of the biotic replacement model by characterizing the intensity of metazoan bioturbation and ecosystem engineering in trace fossil assemblages throughout the latest Ediacaran Nama Group in southern Namibia. The results illustrate a dramatic increase in both bioturbation and ecosystem engineering intensity in the latest Ediacaran, prior to the Cambrian boundary. Moreover, our analyses demonstrate that the highest-impact ecosystem engineering behaviours were present well before the onset of the Cambrian. These data provide the first support for a fundamental prediction of the biotic replacement model, and evidence for a direct link between the early evolution of ecosystem engineering and the extinction of the Ediacara biota.
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Affiliation(s)
- Alison T. Cribb
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
- Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA
| | | | - Bryce Koester
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
- Department of Biodiversity, Drexel University, Philadelphia, PA, 19104, USA
| | - Brandt M. Gibson
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Thomas H. Boag
- Geological Sciences, Stanford University, Stanford, CA 94304, USA
| | - Rachel A. Racicot
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Helke Mocke
- Geological Survey of Namibia, Ministry of Mines and Energy, Windhoek, Namibia
| | - Marc Laflamme
- Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, CanadaL5L 1C6
| | - Simon A. F. Darroch
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
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10
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Gibson BM, Rahman IA, Maloney KM, Racicot RA, Mocke H, Laflamme M, Darroch SAF. Gregarious suspension feeding in a modular Ediacaran organism. SCIENCE ADVANCES 2019; 5:eaaw0260. [PMID: 31223655 PMCID: PMC6584682 DOI: 10.1126/sciadv.aaw0260] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 05/14/2019] [Indexed: 05/29/2023]
Abstract
Reconstructing Precambrian eukaryotic paleoecology is pivotal to understanding the origins of the modern, animal-dominated biosphere. Here, we combine new fossil data from southern Namibia with computational fluid dynamics (CFD) to test between competing feeding models for the Ediacaran taxon Ernietta. In addition, we perform simulations for multiple individuals, allowing us to analyze hydrodynamics of living communities. We show that Ernietta lived gregariously, forming shallow marine aggregations in the latest Ediacaran, 548 to 541 million years (Ma) ago. We demonstrate enhanced vertical mixing of the water column above aggregations and preferential redirection of current into body cavities of downstream individuals. These results support the reconstruction of Ernietta as a macroscopic suspension feeder and also provide a convincing paleoecological advantage to feeding in aggregations analogous to those recognized in many extant marine metazoans. These results provide some of the oldest evidence of commensal facilitation by macroscopic eukaryotes yet recognized in the fossil record.
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Affiliation(s)
| | - Imran A. Rahman
- Oxford University Museum of Natural History, Oxford OX1 3PW, UK
| | - Katie M. Maloney
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Rachel A. Racicot
- Vanderbilt University, Nashville, TN 37235-1805, USA
- WM Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, 925 N Mills Ave., Claremont, CA 91711, USA
| | - Helke Mocke
- Geological Survey of Namibia, National Earth Science Museum, Windhoek, Namibia
| | - Marc Laflamme
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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11
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Affiliation(s)
- Frances S Dunn
- School of Earth Sciences, University of Bristol, Bristol, UK.
| | - Alexander G Liu
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
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