More Like this

1. A diverse Ediacara assemblage survived under low-oxygen conditions

   https://doi.org/10.1038/s41467-022-35012-y  

   Cherry, Lucas B.; Gilleaudeau, Geoffrey J.; Grazhdankin, Dmitriy V.; Romaniello, Stephen J.; Martin, Aaron J.; Kaufman, Alan J. (December 2022, Nature Communications)

   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, δ 238 U 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. 

   more » « less
2. Ediacaran marine animal forests and the ventilation of the oceans

   https://doi.org/10.1016/j.cub.2024.04.059  

   Gutarra, Susana; Mitchell, Emily G; Dunn, Frances S; Gibson, Brandt M; Racicot, Rachel A; Darroch, Simon AF; Rahman, Imran A (May 2024, Current Biology)

   The rise of animals across the Ediacaran–Cambrian transition marked a step-change in the history of life, from a microbially dominated world to the complex macroscopic biosphere we see today.1,2,3 While the importance of bioturbation and swimming in altering the structure and function of Earth systems is well established,4,5,6 the influence of epifaunal animals on the hydrodynamics of marine environments is not well understood. Of particular interest are the oldest “marine animal forests,”7 which comprise a diversity of sessile soft-bodied organisms dominated by the fractally branching rangeomorphs.8,9 Typified by fossil assemblages from the Ediacaran of Mistaken Point, Newfoundland,8,10,11 these ancient communities might have played a pivotal role in structuring marine environments, similar to modern ecosystems,7,12,13 but our understanding of how they impacted fluid flow in the water column is limited. Here, we use ecological modeling and computational flow simulations to explore how Ediacaran marine animal forests influenced their surrounding environment. Our results reveal how organism morphology and community structure and composition combined to impact vertical mixing of the surrounding water. We find that Mistaken Point communities were capable of generating high-mixing conditions, thereby likely promoting gas and nutrient transport within the “canopy.” This mixing could have served to enhance local-scale oxygen concentrations and redistribute resources like dissolved organic carbon. Our work suggests that Ediacaran marine animal forests may have contributed to the ventilation of the oceans over 560 million years ago, well before the Cambrian explosion of animals. 

   more » « less
3. The Shibantan Lagerstätte: insights into the Proterozoic–Phanerozoic transition

   https://doi.org/10.1144/jgs2020-135  

   Xiao, Shuhai; Chen, Zhe; Pang, Ke; Zhou, Chuanming; Yuan, Xunlai (December 2020, Journal of the Geological Society)

   null (Ed.)

   The Shibantan Lagerstätte (551–543 Ma) in the Yangtse Gorges area in South China is one of the best-known examples of terminal Ediacaran fossil assemblages preserved in marine carbonate rocks. Taxonomically dominated by benthic organisms, the Shibantan Lagerstätte preserves various photoautotrophs, biomineralizing tubular fossils, Ediacara-type macrofossils (including rangeomorphs, arboreomorphs, erniettomorphs, palaeopascichnids, a possible dickinsoniomorph, the mobile bilaterian Yilingia and soft-bodied tubular fossils), abundant ichnofossils and a number of problematic and dubious fossils. Shibantan fossils provide intriguing insights into ecological interactions among mobile bilaterians, sessile benthic Ediacara-type organisms and microbial mats, thus offering important data to test various hypotheses accounting for the decline of the Ediacara biota and the concurrent expansion of bilaterian bioturbation and mobility across the Proterozoic–Phanerozoic transition. 

   more » « less
4. Lagerstätten: Ediacaran soft-bodied fossils from the Nama Group

   https://doi.org/10.1144/jgs2024-288  

   Darroch, S_A F; Mocke, H; Gibson, B M; Tingle, K E; Schiffbauer, J D; Nelson, L L; Laflamme, M (October 2025, Journal of the Geological Society)

   The Nama Group of Namibia and South Africa preserves an extraordinary record of marine ecosystems existing in the lastc. 15 myr of the Ediacaran, comprising enigmatic and soft-bodied fossils that are part of the first major radiation of macroscopic life. Since their description at the beginning of the 20th century these fossils have played an important role in debates surrounding the affinities of iconic Ediacaran fossil groups, and ash beds preserved throughout the succession have been crucial to understanding rates and patterns of early animal evolution. Fossils preserved in varying contexts have allowed for detailed reconstructions of Ediacaran palaeobiology, and geochemical analyses provide a window into understanding the controls on Ediacaran taphonomic pathways, including crucial, and potentially widespread, roles played by clay minerals in exceptional fossil preservation. 

   more » « less
5. Localized and Transient Oxygenation of Shallow Oceans of Southwestern Laurentia at the Ediacaran–Cambrian Boundary

   https://doi.org/10.1111/gbi.70039  

   Chanchai, Watsawan; Nelson, Lyle L; Smith, Emily F; Hardisty, Dalton S; Lonsdale, Mary C; Burke, Janet E; Lau, Kimberly V (January 2026, Geobiology)

   ABSTRACT The Ediacaran–Cambrian boundary, which precedes one of the most significant biotic diversification events in Earth's history, is associated with a global negative carbon isotope excursion termed the BAsal Cambrian carbon isotope Excursion (BACE). Late Ediacaran and early Cambrian changes in shallow marine oxygenation have been proposed to relate to the BACE as well as metazoan extinction and radiation. However, reconstructing paleoredox conditions at the Ediacaran–Cambrian boundary is limited by challenges in correlating carbonate strata due to sparse stratigraphic markers and non‐unique chemostratigraphic correlations. These imprecise correlations have led to uncertainty in how redox changes across the BACE should be interpreted in relation to broader regional and global environmental patterns. Here, we present redox reconstructions from southwestern Laurentian carbonate successions that record the BACE, including the limestone‐dominated Deep Spring Formation, southwestern USA, and the dolostone‐dominated La Ciénega Formation, northern Mexico. We combine local (carbonate‐bound iodine, I/(Ca + Mg) and cerium anomaly, Ce/Ce*) and global (carbonate‐associated uranium isotopes, δ²³⁸U_carb) redox proxies to investigate marine oxygenation in relation to the BACE. Contrary to previous suggestions that a global ocean oxygenation event coincided with the BACE, we do not observe a shift in δ²³⁸U_carbconcurrent with the carbon isotope excursion in either section. The δ²³⁸U_carbvalues differ between two sections, likely reflecting distinct diagenetic offsets attributed to different diagenetic U reduction, but together provide a minimal constraint on the carbonate δ²³⁸U value and suggest a more anoxic ocean compared to today. The local proxy results at both sites suggest widespread low‐oxygen surface waters with a transient and localized interval of shallow marine oxygenation at one site that coincides with the nadir of the BACE. Persistently low I/(Ca + Mg) ratios, below values observed in today's oxygenated oceans, suggest a broadly redox‐stratified surface ocean. Negative Ce anomalies in the La Ciénega Formation were recorded during the BACE nadir, suggesting a short‐lived interval of local oxygenation within otherwise low‐oxygen conditions. In sum, we do not find evidence for major, widespread oxygenation coincident with the BACE, but a continuation of low‐oxygen conditions punctuated by a short‐lived oxygenation event in the shallow oceans. These brief fluctuations in oxygen levels, in turn, may have played a role in the onset of behavioral complexity among bilaterian invertebrates during this critical transition. 

   more » « less