1
|
Gibson BM, Schiffbauer JD, Wallace AF, Darroch SAF. The role of iron in the formation of Ediacaran 'death masks'. GEOBIOLOGY 2023; 21:421-434. [PMID: 36843397 DOI: 10.1111/gbi.12551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 01/30/2023] [Accepted: 02/12/2023] [Indexed: 06/13/2023]
Abstract
The Ediacara biota are an enigmatic group of Neoproterozoic soft-bodied fossils that mark the first major radiation of complex eukaryotic and macroscopic life. These fossils are thought to have been preserved via pyritic "death masks" mediated by seafloor microbial mats, though little about the chemical constraints of this preservational pathway is known, in particular surrounding the role of bioavailable iron in death mask formation and preservational fidelity. In this study, we perform decay experiments on both diploblastic and triploblastic animals under a range of simulated sedimentary iron concentrations, in order to characterize the role of iron in the preservation of Ediacaran organisms. After 28 days of decay, we demonstrate the first convincing "death masks" produced under experimental laboratory conditions composed of iron sulfide and probable oxide veneers. Moreover, our results demonstrate that the abundance of iron in experiments is not the sole control on death mask formation, but also tissue histology and the availability of nucleation sites. This illustrates that Ediacaran preservation via microbial death masks need not be a "perfect storm" of paleoenvironmental porewater and sediment chemistry, but instead can occur under a range of conditions.
Collapse
Affiliation(s)
- Brandt M Gibson
- Department of Earth & Environmental Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - James D Schiffbauer
- Department of Geological Sciences, University of Missouri, Columbia, Missouri, USA
- X-ray Microanalysis Core Facility, University of Missouri, Columbia, Missouri, USA
| | - Adam F Wallace
- Department of Geological Sciences, University of Delaware, Newark, Delaware, USA
| | - Simon A F Darroch
- Department of Earth & Environmental Sciences, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
2
|
A diverse Ediacara assemblage survived under low-oxygen conditions. Nat Commun 2022; 13:7306. [PMID: 36435820 PMCID: PMC9701187 DOI: 10.1038/s41467-022-35012-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 11/15/2022] [Indexed: 11/28/2022] Open
Abstract
The Ediacaran biota were soft-bodied organisms, many with enigmatic phylogenetic placement and ecology, living in marine environments between 574 and 539 million years ago. Some studies hypothesize a metazoan affinity and aerobic metabolism for these taxa, whereas others propose a fundamentally separate taxonomic grouping and a reliance on chemoautotrophy. To distinguish between these hypotheses and test the redox-sensitivity of Ediacaran organisms, here we present a high-resolution local and global redox dataset from carbonates that contain in situ Ediacaran fossils from Siberia. Cerium anomalies are consistently >1, indicating that local environments, where a diverse Ediacaran assemblage is preserved in situ as nodules and carbonaceous compressions, were pervasively anoxic. Additionally, δ238U values match other terminal Ediacaran sections, indicating widespread marine euxinia. These data suggest that some Ediacaran biotas were tolerant of at least intermittent anoxia, and thus had the capacity for a facultatively anaerobic lifestyle. Alternatively, these soft-bodied Ediacara organisms may have colonized the seafloor during brief oxygenation events not recorded by redox proxy data. Broad temporal correlations between carbon, sulfur, and uranium isotopes further highlight the dynamic redox landscape of Ediacaran-Cambrian evolutionary events.
Collapse
|
3
|
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.
Collapse
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
| | | |
Collapse
|
4
|
Duda JP, Love GD, Rogov VI, Melnik DS, Blumenberg M, Grazhdankin DV. Understanding the geobiology of the terminal Ediacaran Khatyspyt Lagerstätte (Arctic Siberia, Russia). GEOBIOLOGY 2020; 18:643-662. [PMID: 32881267 DOI: 10.1111/gbi.12412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 06/16/2020] [Accepted: 07/30/2020] [Indexed: 06/11/2023]
Abstract
The Khatyspyt Lagerstätte (~544 Ma, Russia) provides a valuable window into late Ediacaran Avalon-type ecosystems with rangeomorphs, arboreomorphs, and mega-algae. Here, we tackle the geobiology of this Lagerstätte by the combined analysis of paleontological features, sedimentary facies, and lipid biomarkers. The Khatyspyt Formation was deposited in carbonate ramp environments. Organic matter (0.12-2.22 wt.% TOC) displays characteristic Ediacaran biomarker features (e.g., eukaryotic steranes dominated by the C29 stigmastane). Some samples contain a putative 2-methylgammacerane that was likely sourced by ciliates and/or bacteria. 24-isopropylcholestane and 26-methylstigmastane are consistently scarce (≤0.4% and ≤0.2% of ∑C27-30 regular steranes, respectively). Thus, Avalon-type organisms occupied different niches than organisms capable of directly synthesizing C30 sterane precursors among their major lipids. Relative abundances of eukaryotic steranes and bacterial hopanes (sterane/hopane ratios = 0.07-0.30) demonstrate oligotrophic and bacterially dominated marine environments, similar to findings from other successions with Ediacara-type fossils. Ediacara-type fossils occur in facies characterized by microbial mats and biomarkers indicative for a stratified marine environment with normal-moderate salinities (moderate-high gammacerane index of 2.3-5.7; low C35 homohopane index of 0.1-0.2). Mega-algae, in contrast, are abundant in facies that almost entirely consist of allochthonous event layers. Biomarkers in these samples indicate a non-stratified marine environment and normal salinities (low gammacerane index of 0.6-0.8; low C35 homohopane index of 0.1). Vertical burrowers occur in similar facies but with biomarker evidence for stratification in the water column or around the seafloor (high gammacerane index of 5.6). Thus, the distribution of macro-organisms and burrowers was controlled by various, dynamically changing environmental factors. It appears likely that dynamic settings like the Khatyspyt Lagerstätte provided metabolic challenges for sustenance and growth which primed eukaryotic organisms to cope with changing environmental habitats, allowing for a later diversification and expansion of complex macroscopic life in the marine realm.
Collapse
Affiliation(s)
- Jan-Peter Duda
- Department of Earth and Planetary Sciences, University of California, Riverside, CA, USA
- Geobiology Group, Geoscience Centre, University of Göttingen, Göttingen, Germany
| | - Gordon D Love
- Department of Earth and Planetary Sciences, University of California, Riverside, CA, USA
| | - Vladimir I Rogov
- Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch Russian Academy of Sciences, Novosibirsk, Russia
| | - Dmitry S Melnik
- Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
| | - Martin Blumenberg
- Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany
| | - Dmitriy V Grazhdankin
- Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
| |
Collapse
|
5
|
Tarhan LG, Droser ML, Cole DB, Gehling JG. Ecological Expansion and Extinction in the Late Ediacaran: Weighing the Evidence for Environmental and Biotic Drivers. Integr Comp Biol 2019; 58:688-702. [PMID: 29718307 DOI: 10.1093/icb/icy020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The Ediacara Biota, Earth's earliest communities of complex, macroscopic, multicellular organisms, appeared during the late Ediacaran Period, just prior to the Cambrian Explosion. Ediacara fossil assemblages consist of exceptionally preserved soft-bodied forms of enigmatic morphology and affinity which nonetheless represent a critical stepping-stone in the evolution of complex animal ecosystems. The Ediacara Biota has historically been divided into three successive Assemblages-the Avalon, the White Sea, and the Nama. Although the oldest (Avalon) Assemblage documents the initial appearance of several groups of Ediacara taxa, the two younger (White Sea and Nama) Assemblages record a particularly striking suite of ecological innovations, including the appearance of diverse Ediacara body plans-in tandem with the rise of bilaterian animals-as well as the emergence of novel ecological strategies such as movement, sexual reproduction, biomineralization, and the development of dense, heterogeneous benthic communities. Many of these ecological innovations appear to be linked to adaptations to heterogeneous substrates and shallow and energetic marine settings. In spite of these innovations, the majority of Ediacara taxa disappear by the end of the Ediacaran, with interpretations for this disappearance historically ranging from the closing of preservational windows to environmentally or biotically mediated extinction. However, in spite of the unresolved affinity and eventual extinction of individual Ediacara taxa, these distinctive ecological strategies persist across the Ediacaran-Cambrian boundary and are characteristic of younger animal-dominated communities of the Phanerozoic. The late Ediacaran emergence of these strategies may, therefore, have facilitated subsequent radiations of the Cambrian. In this light, the Ediacaran and Cambrian Periods, although traditionally envisioned as separate worlds, are likely to have been part of an ecological and evolutionary continuum.
Collapse
Affiliation(s)
- Lidya G Tarhan
- Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA
| | - Mary L Droser
- Department of Earth Sciences, University of California, 900 University Avenue, Riverside, CA 92521, USA
| | - Devon B Cole
- Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA
| | - James G Gehling
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia.,University of Adelaide, North Terrace, Adelaide, South Australia 5000, Australia
| |
Collapse
|