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1. Rebuilding Earth’s first skeletal animals: the original morphology of Corumbella (Ediacaran, Brazil)

   https://doi.org/10.1098/rsos.250206  

   Becker-Kerber, Bruno; Ortega-Hernández, Javier; Schiffbauer, James D; Lerosey-Aubril, Rudy; Warren, Lucas Verissimo; Simões, Marcello Guimarães; del_Mouro, Lucas; Rodella, Cristiane Barbieri; Basei, Miguel_Angelo Stipp; Archilha, Nathaly Lopes (May 2025, Royal Society Open Science)

   The evolutionary onset of animal biomineralization in the late Ediacaran (ca555–538 Ma) is marked by the global appearance of enigmatic tubular fossils with unresolved phylogenetic relationships. Among these,Corumbella wernerifrom the Tamengo Formation (Corumbá Group, Brazil) has been variously interpreted as affiliated with cnidarians or bilaterians. Using synchrotron imaging and machine learning, we analysed new specimens ofC. wernerito reconstruct their original skeletal organization. Our findings reveal thatCorumbella’s tubes were originally conico-cylindrical. Large individuals ofCorumbella, including less compacted specimens, and compression experiments with modern annelid tubes all indicate that previous reconstructions of a quadrate outline and midline features were misled by taphonomic artefacts. We also show that the wall ofCorumbellais composed of a single layer of ring-shaped elements. Unlike the fourfold symmetry of scyphozoans or the complex cataphract-like structures of Cambrian bilaterians (e.g. halkieriids, tommotiids and wiwaxiids),Corumbelladisplays structural similarities with other late Ediacaran corumbellomorphs, such asCostatubus. These taxa exhibit a distinctive barrel-on-barrel tube construction, with modular elements stacked on each other rather than nested. Our findings redefineCorumbella’s morphology and phylogenetic affinities, contributing to a broader understanding of early biomineralizing metazoans and their ecological roles in the Ediacaran biosphere. 

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2. Archaeichnium haughtoni : a robust burrow lining from the Ediacaran–Cambrian transition of Namibia

   https://doi.org/10.1002/spp2.1546  

   Turk, Katherine A.; Pulsipher, Mikaela A.; Bergh, Eugene; Laflamme, Marc; Darroch, Simon A. F. (January 2024, Papers in Palaeontology)

   Abstract Following various assignments to Archaeocyatha, worm tubes, and finallyincertae sedis, the enigmatic Ediacaran–Cambrian taxonArchaeichnium haughtonihas in recent years come to represent somewhat of a wastebasket taxon to which the indeterminate tapering tubular forms common across this interval are assigned. This ‘catch‐all’ status has been aided in part by both suboptimal specimen photography and the temporary loss of the holotype after its second redescription in 1978. Recent rediscovery of theA. haughtoniholotype in the collections of the Iziko South African Museum in Cape Town has enabled a much‐needed re‐assessment of this critical and cryptic taxon, with results suggesting that this material from the latest Ediacaran or earliest Cambrian of Namibia is among the earliest fossil record examples of marine worm burrow linings, and the oldest examples of linings robust enough to withstand exhumation and current transport. These traces indicate the emergence of this important animalian ecosystem engineering behaviour closer to the Ediacaran–Cambrian boundary than previously thought. 

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3. Priapulid neoichnology, ecosystem engineering, and the Ediacaran–Cambrian transition

   https://doi.org/10.1111/pala.12721  

   Turk, Katherine_A; Wehrmann, Achim; Laflamme, Marc; Darroch, Simon_A_F (August 2024, Palaeontology)

   Abstract The evolutionary rise of powerful new ecosystem engineering impacts is thought to have played an important role in driving waves of biospheric change across the Ediacaran–Cambrian transition (ECT;c. 574–538 Ma). Among the most heavily cited of these is bioturbation (organism‐driven sediment disturbance) as these activities have been shown to have critical downstream geobiological impacts. In this regard priapulid worms are crucial; trace fossils thought to have been left by priapulan‐grade animals are now recognized as appearing shortly before the base of the Cambrian and represent some of the earliest examples of bed‐penetrative bioturbation. Understanding the ecosystem engineering impacts of priapulids may thus be key to reconstructing drivers of the ECT. However, priapulids are rare in modern benthic ecosystems, and thus comparatively little is known about the behaviours and impacts associated with their burrowing. Here, we present the early results of neoichnological experiments focused on understanding the ecosystem engineering impacts of priapulid worms. We observe for the first time a variety of new burrowing behaviours (including the formation of linked burrow networks and long in‐burrow residence times) hinting at larger ecosystem engineering impacts in this group than previously thought. Finally, we identify means by which these results may contribute to our understanding of tracemakers across the ECT, and the role they may have had in shaping the latest Ediacaran and earliest Cambrian biosphere. 

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4. Late Neoproterozoic – early Paleozoic basin evolution in the Coal Creek inlier of Yukon, Canada: implications for the tectonic evolution of northwestern Laurentia

   https://doi.org/10.1139/cjes-2020-0132  

   Busch, James F.; Rooney, Alan D.; Meyer, Edward E.; Town, Caleb F.; Moynihan, David P.; Strauss, Justin V. (April 2021, Canadian Journal of Earth Sciences)

   null (Ed.)

   The age and nature of the Neoproterozoic – early Paleozoic rift–drift transition has been interpreted differently along the length of the North American Cordillera. The Ediacaran “upper” group (herein elevated to the Rackla Group) of the Coal Creek inlier, Yukon, Canada, represents a key succession to reconstruct the sedimentation history of northwestern Laurentia across the Precambrian–Cambrian boundary and elucidate the timing of active tectonism during the protracted breakup of the supercontinent Rodinia. These previously undifferentiated late Neoproterozoic – early Paleozoic map units in the Coal Creek inlier are herein formally defined as the Lone, Cliff Creek, Mount Ina, Last Chance, Shade, and Shell Creek formations. New sedimentological and stratigraphic data from these units is used to reconstruct the depositional setting. In the Last Chance Formation, chemostratigraphic observations indicate a ca. 5‰ δ 13 C carb gradient coincident with the globally recognized ca. 574–567 Ma Shuram carbon isotope excursion. Map and stratigraphic relationships in the overlying Shell Creek Formation provide evidence for latest Ediacaran – middle Cambrian tilting and rift-related sedimentation. This provides evidence for active extension through the Cambrian Miaolingian Series in northwestern Canada, supporting arguments for a multiphase and protracted breakup of Rodinia. 

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5. Functional morphology of the Ediacaran organism Tribrachidium heraldicum

   https://doi.org/10.1017/pab.2024.24  

   Olaru, A; Gutarra-Diaz, S; Racicot, R A; Dunn, F S; Rahman, I A; Wang, Z; Darroch, S_A F; Gibson, B M (October 2024, Paleobiology)

   Abstract Tribrachidium heraldicumis an Ediacaran body fossil characterized by triradial symmetry. Previous work has suggested that the anatomy ofTribrachidiumwas conducive to passive suspension feeding; however, these analyses used an inaccurate model and a relatively simple set of simulations. Using computational fluid dynamics, we explore the functional morphology ofTribrachidiumin unprecedented detail by gauging how the presence or absence of distinctive anatomical features (e.g., apical pits and arms) affects flow patterns. Additionally, we map particle pathways, quantify deposition rates at proposed feeding sites, and assess gregarious feeding habits to more fully reconstruct the lifestyle of this enigmatic taxon. Our results provide strong support for interpretingTribrachidiumas a macroscopic suspension feeder, with the apical pits representing loci of particle collection (and possibly ingestion) and the triradial arms representing morphological adaptations for interrupting flow and inducing settling. More speculatively, we suggest that the radial grooves may represent ciliated pathways through which food particles accumulating in the wake of the organism were transported toward the apical pits. Finally, our results allow us to generate new functional hypotheses for other Ediacaran taxa with a triradial body plan. This work refines our understanding of the appearance of suspension feeding in shallow-water paleoenvironments, with implications for the radiation of Metazoa across the Ediacaran/Cambrian boundary. 

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