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Anderson RP, Woltz CR, Tosca NJ, Porter SM, Briggs DEG. Fossilisation processes and our reading of animal antiquity. Trends Ecol Evol 2023; 38:1060-1071. [PMID: 37385847 DOI: 10.1016/j.tree.2023.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 05/19/2023] [Accepted: 05/22/2023] [Indexed: 07/01/2023]
Abstract
Estimates for animal antiquity exhibit a significant disconnect between those from molecular clocks, which indicate crown animals evolved ∼800 million years ago (Ma), and those from the fossil record, which extends only ∼574 Ma. Taphonomy is often held culpable: early animals were too small/soft/fragile to fossilise, or the circumstances that preserve them were uncommon in the early Neoproterozoic. We assess this idea by comparing Neoproterozoic fossilisation processes with those of the Cambrian and its abundant animal fossils. Cambrian Burgess Shale-type (BST) preservation captures animals in mudstones showing a narrow range of mineralogies; yet, fossiliferous Neoproterozoic mudstones rarely share the same mineralogy. Animal fossils are absent where BST preservation occurs in deposits ≥789 Ma, suggesting a soft maximum constraint on animal antiquity.
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Affiliation(s)
- Ross P Anderson
- Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK; All Souls College, University of Oxford, Oxford, OX1 4AL, UK.
| | - Christina R Woltz
- Department of Earth Science, University of California at Santa Barbara, Santa Barbara, CA 93106, USA; Department of Earth and Planetary Sciences, Stanford University, Stanford, CA, 94305, USA
| | - Nicholas J Tosca
- Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Susannah M Porter
- Department of Earth Science, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
| | - Derek E G Briggs
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511, USA; Yale Peabody Museum, Yale University, New Haven, CT 06520, USA
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Bobrovskiy I, Nagovitsyn A, Hope JM, Luzhnaya E, Brocks JJ. Guts, gut contents, and feeding strategies of Ediacaran animals. Curr Biol 2022; 32:5382-5389.e3. [PMID: 36417903 DOI: 10.1016/j.cub.2022.10.051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 06/16/2022] [Accepted: 10/25/2022] [Indexed: 11/23/2022]
Abstract
The oldest animals appear in the fossil record among Ediacara biota communities. They prelude animal-dominated ecosystems of the Phanerozoic and may hold clues to the appearance of modern animal phyla in the Cambrian explosion. However, little is known about the phylogeny of the Ediacaran organisms and even less about their diet and feeding behavior.1,2,3 An exception is mollusc-like Kimberella, for which a fossilized gut, feeding traces, and even potential coprolites have been found.4,5 By contrast, Ediacaran organic-walled tubes, such as Sabellidites and Calyptrina, are thought to belong to tube worms comparable with modern Siboglinidae that have no gut but gain their nutrition from symbiotic bacteria.6,7 Here, we examine the gut contents of Ediacaran animals using biomarker molecules. We show that 558-million-year (Ma)-old tube worm-like Calyptrina and mollusc-like Kimberella possessed a gut and shared a diet of green algae and bacteria. Despite their ancient age, sterol metabolism within the gut of both organisms was already comparable to extant invertebrates.8Dickinsonia, one of the key Ediacaran animals, show no traces of dietary molecules, indicating a different feeding mode and possible external digestion analogous to modern Placozoa. Lipid biomarkers uncover a range of feeding strategies in Ediacaran communities, highlighting true eumetazoan physiology of some Ediacaran animals.
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Affiliation(s)
- Ilya Bobrovskiy
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia.
| | | | - Janet M Hope
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
| | - Ekaterina Luzhnaya
- Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow 117997, Russia
| | - Jochen J Brocks
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia.
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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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Abstract
Earth's earliest fossils of complex macroscopic life are recorded in Ediacaran-aged siliciclastic deposits as exceptionally well-preserved three-dimensional casts and molds, known as "Ediacara-style" preservation. Ediacara-style fossil assemblages commonly include both macrofossils of the enigmatic Ediacara Biota and associated textural impressions attributed to microbial matgrounds that were integral to the ecology of Ediacara communities. Here, we use an experimental approach to interrogate to what extent the presence of mat-forming microorganisms was likewise critical to the Ediacara-style fossilization of these soft-bodied organisms. We find evidence that biofilms can play an instrumental role in fostering fossilization. Rapid silica precipitation associated with macroorganism tissues is enhanced in the presence of mat- and biofilm-forming microorganisms. These results indicate that the occurrence of microbial mats and biofilms may have strongly shaped the preservational window for Ediacara-style fossils associated with early diagenetic silica cements, and therefore influenced the distribution and palaeoecological interpretation of the Ediacara Biota fossil record.
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Evans SD, Gehling JG, Erwin DH, Droser ML. Ediacara growing pains: Modular addition and development in Dickinsonia costata. PALEOBIOLOGY 2021; 97:10.1017/pab.2021.31. [PMID: 35001986 PMCID: PMC8740542 DOI: 10.1017/pab.2021.31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Constraining patterns of growth using directly observable and quantifiable characteristics can reveal a wealth of information regarding the biology of the Ediacara Biota - the oldest macroscopic, complex community forming organisms in the fossil record. However, these rely on individuals captured at an instant in time at various growth stages, and so different interpretations can be derived from the same material. Here we leverage newly discovered and well-preserved Dickinsonia costata Sprigg 1947 from South Australia, combined with hundreds of previously described specimens, to test competing hypotheses for the location of module addition. We find considerable variation in the relationship between the total number of modules and body size that cannot be explained solely by expansion and contraction of individuals. Patterns derived assuming new modules differentiated at the anterior result in numerous examples where the oldest module(s) must decrease in size with overall growth, potentially falsifying this hypothesis. Observed polarity as well as the consistent posterior location of defects and indentations support module formation at this end in D. costata. Regardless, changes in repeated units with growth share similarities with those regulated by morphogen gradients in metazoans today, suggesting that these genetic pathways were operating in Ediacaran animals.
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Affiliation(s)
- Scott D Evans
- Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - James G Gehling
- South Australia Museum, Adelaide, South Australia 5000, Australia
| | - Douglas H Erwin
- Department of Paleobiology MRC-121, National Museum of Natural History, Washington, DC 20013-7012, USA
| | - Mary L Droser
- Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
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McIlroy D, Dufour SC, Taylor R, Nicholls R. The role of symbiosis in the first colonization of the seafloor by macrobiota: Insights from the oldest Ediacaran biota (Newfoundland, Canada). Biosystems 2021; 205:104413. [PMID: 33794297 DOI: 10.1016/j.biosystems.2021.104413] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/19/2021] [Accepted: 03/20/2021] [Indexed: 01/23/2023]
Abstract
The earliest record of animal life comes from the Ediacaran of Newfoundland, including dm scale fossil organisms, most of which are inferred to have been epibenthic immotile eumetazoans. This work introduces the palaeobiology of the major fossil groups in the Newfoundland assemblages including strange fractal-like taxa and addresses some of biogeochemical challenges such as sulfide buildup that could most easily have been overcome by symbiogenesis. Specifically, the epibenthic reclining nature of some of the Ediacaran biota-with their fractal-like high surface area lower surfaces-are considered to have been well designed for gaining nutriment from chemosynthetic, sulfur-oxidizing bacteria. This view constitutes a shift away from the view that most of the biota were anomalously large osmotrophs.
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Affiliation(s)
- Duncan McIlroy
- Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada; Bonne Bay Marine Station, Memorial University of Newfoundland, Norris Point, PO Box 69, A0K 3V0, Canada.
| | - Suzanne C Dufour
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada
| | - Rod Taylor
- Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada
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The role of volcanic-derived clays in the preservation of Ediacaran biota from the Itajaí Basin (ca. 563 Ma, Brazil). Sci Rep 2021; 11:5013. [PMID: 33658558 PMCID: PMC7930025 DOI: 10.1038/s41598-021-84433-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 02/05/2021] [Indexed: 11/22/2022] Open
Abstract
The early evolution of metazoans has been reconstructed by studies on exceptionally preserved molds in siliciclastic rocks from the Ediacaran Period. However, there remains considerable controversy regarding the formation mechanisms of this unusual ‘Ediacaran-style’ preservation. Proposed hypotheses usually include early authigenesis of minerals, but evidence for this is scarce. In a recently discovered deposit of Ediacaran biota in Brazil, we show that the classic moldic preservation is related to clay mineral authigenesis. Specifically, these clays originated from the alteration of original pyroclastic sediments, likely enhanced by microbial activity, leading to early illitization and morphological templating of the fossiliferous surfaces at a micrometric scale. Such high-fidelity preservation was made possible by rapid burial during volcanic events and the in-situ templating of tissue by clays via microbially-mediated mineralization. This newly described Lagerstätte demonstrates that a number of minerals can facilitate preservation, and that perhaps ‘Ediacaran-style’ preservation result from different processes leading to the same broad style of preservation.
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Droser ML, Tarhan LG, Evans SD, Surprenant RL, Gehling JG. Biostratinomy of the Ediacara Member (Rawnsley Quartzite, South Australia): implications for depositional environments, ecology and biology of Ediacara organisms. Interface Focus 2020; 10:20190100. [PMID: 32642047 DOI: 10.1098/rsfs.2019.0100] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2020] [Indexed: 11/12/2022] Open
Abstract
The Precambrian Ediacara Biota-Earth's earliest fossil record of communities of macroscopic, multicellular organisms-provides critical insights into the emergence of complex life on our planet. Excavation and reconstruction of nearly 300 m2 of fossiliferous bedding planes in the Ediacara Member of the Rawnsley Quartzite, at the National Heritage Ediacara fossil site Nilpena in South Australia, have permitted detailed study of the sedimentology, taphonomy and palaeoecology of Ediacara fossil assemblages. Characterization of Ediacara macrofossils and textured organic surfaces at the scale of facies, bedding planes and individual specimens has yielded unprecedented insight into the manner in which the palaeoenvironmental settings inhabited by Ediacara communities-particularly hydrodynamic conditions-influenced the aut- and synecology of Ediacara organisms, as well as the morphology and assemblage composition of Ediacara fossils. Here, we describe the manner in which environmental processes mediated the development of taphofacies hosting Ediacara fossil assemblages. Using two of the most common Ediacara Member fossils, Arborea and Dickinsonia, as examples, we delineate criteria that can be used to distinguish between ecological, environmental and biostratinomic signals and reconstruct how interactions between these processes have distinctively shaped the Ediacara fossil record.
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Affiliation(s)
- Mary L Droser
- Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
| | - Lidya G Tarhan
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
| | - Scott D Evans
- Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
| | - Rachel L Surprenant
- Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
| | - James G Gehling
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
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Evans SD, Gehling JG, Droser ML. Slime travelers: Early evidence of animal mobility and feeding in an organic mat world. GEOBIOLOGY 2019; 17:490-509. [PMID: 31180184 DOI: 10.1111/gbi.12351] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 05/10/2019] [Accepted: 05/15/2019] [Indexed: 06/09/2023]
Abstract
Mobility represents a key innovation in the evolution of complex animal life. The ability to move allows for the exploration of new food sources, escapes from unfavorable environmental conditions, enhanced ability to exchange genetic material, and is one of the major reasons for the diversity and success of animal life today. The oldest widely accepted trace fossils of animal mobility are found in Ediacaran-aged rocks (635-539 Ma). The earliest definitive evidence for movement associated with exploitation of resources for feeding occurs in the White Sea assemblage of the Ediacara Biota-macroscopic, soft-bodied fossils of Ediacaran age. Here, we evaluate potential support for mobility in dickinsoniomorphs, presenting new data regarding abundant Dickinsonia and associated trace fossils from the Ediacara Member, South Australia. Results quantitatively demonstrate that Dickinsonia was capable of mobility on relatively short, ecological timescales. This organism was bilaterally symmetrical, likely moved via muscular peristalsis, and left trace fossils due to active removal of the organic mat related to feeding. Analogous structures associated with Yorgia indicate that it was also mobile and fed in a similar manner. Morphological evidence suggests that two other modular taxa, Andiva and Spriggina, were able to move but did not feed in a manner that impacted the organic mat. Together, these data suggest that mobility was present in multiple disparate bilaterally symmetrical Ediacaran taxa.
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Affiliation(s)
- Scott D Evans
- Department of Earth Sciences, University of California at Riverside, Riverside, California
| | - James G Gehling
- South Australia Museum, Adelaide, South Australia, Australia
| | - Mary L Droser
- Department of Earth Sciences, University of California at Riverside, Riverside, California
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