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1. Molecular Memories of a Cambrian Fossil

   https://doi.org/10.1525/abt.2020.82.9.586  

   Babaian, Caryn; Kumar, Sudhir (November 2020, The American Biology Teacher)

   null (Ed.)

   Evolutionary evidence is important scientific background for appreciating the theory of evolution. We describe a STEAM-based lesson plan that uses paleontological drawings and a modern evolutionary database to explore and understand fossil, morphological, and molecular evidence. Together, with a focus on arthropods and the Cambrian explosion, students experience a heuristic process common in scientific reasoning, guiding them toward practices that synthesize knowledge and invite questioning in the life sciences. 

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2. Musculature of an Early Cambrian cycloneuralian animal

   https://doi.org/10.1098/rspb.2023.1803  

   Zhang, Huaqiao; Xiao, Shuhai; Eriksson, Mats E; Duan, Baichuan; Maas, Andreas (October 2023, Proceedings of the Royal Society B: Biological Sciences)

   Cycloneuralians are ecdysozoans with a fossil record extending to the Early Cambrian Fortunian Age and represented mostly by cuticular integuments. However, internal anatomies of Fortunian cycloneuralians are virtually unknown, hampering our understanding of their functional morphology and phylogenetic relationships. Here we report the exceptional preservation of cycloneuralian introvert musculature in Fortunian rocks of South China. The musculature consists of an introvert body-wall muscular grid of four circular and 36 radially arranged longitudinal muscle bundles, as well as an introvert circular muscle associated with 19 roughly radially arranged, short retractors. Collectively, these features support at least a scalidophoran affinity, and the absence of muscles associated with a mouth cone and scalids further indicates a priapulan affinity. As in modern scalidophorans, the fossil musculature, and particularly the introvert circular muscle retractors, may have controlled introvert inversion and facilitated locomotion and feeding. This work supports the evolution of scalidophoran-like or priapulan-like introvert musculature in cycloneuralians at the beginning of the Cambrian Period. 

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3. Deciphering trophic interactions in a mid-Cambrian assemblage

   https://doi.org/10.1016/j.isci.2021.102271  

   Swain, Anshuman; Devereux, Matthew; Fagan, William F. (April 2021, iScience)

   null (Ed.)
4. Gill grooming in middle Cambrian and Late Ordovician trilobites

   https://doi.org/10.1017/S001675682300002X  

   Hou, Jin-bo; Hughes, Nigel C.; Hopkins, Melanie J. (May 2023, Geological Magazine)

   Abstract Efficient extraction of oxygen from ambient waters played a critical role in the development of early arthropods. Maximizing gill surface area enhanced oxygen uptake ability but, with gills necessarily exposed to the external environment, also presented the issue of gill contamination. Here we document setae inserted on the dorsal surface of walking legs of the benthic-dwelling middle CambrianOlenoides serratusand on the gill shaft of the Late OrdovicianTriarthrus eatoni. Based on their physical positions relative to gill filaments, we interpret these setae to have been used to groom the gills, removing particles trapped among the filaments. The coordination between setae and gill filaments is comparable to that seen among modern crustaceans, which use a diverse set of setae-bearing appendages to penetrate between gill filaments when grooming. Grooming is known relatively early in trilobite evolutionary history and would have enhanced gill efficiency by maximizing the surface area for oxygen uptake. 

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5. 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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