Cambrian fossils illuminate the ancestral nervous system of chelicerates (UPDATED)

January 21, 2022
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We start off 2022 with a new Open Access publication in Nature Communications describing the exceptionally preserved nervous system of the soft-bodied euarthropod Mollisonia symmetrica from the mid-Cambrian Burgess Shale, featuring some stunning material from our own Invertebrate Paleontology collections at the Museum of Comparative Zoology and the Smithsonian Institution. Mollisonia reveals fine details including optic nerves, a ganglionted ventral nerve cord and segmental nerves, all of which inform the ancestral neuroanatomical  organization of chelicerates (e.g. extant horseshoe crabs and arachnids). The results suggest a complex scenario for the internal anatomy of chelicerates during their early evolutionary history, and has implications for understanding the affinity of other major groups of Cambrian euarthropods, such as the megacheirans. Thanks to the Wetmore Colles Grant for supporting the publication of this work. 

Also check out a less technical piece about the significance of this study at the Nature Portfolio Ecology & Evolution Community Blog. 

On a rush? You can also listen an eight minute-long interview with Bob McDonald in the Canadian radio program Quirks & Quarks!

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Specimens of Mollisonia symmetrica from the 508-million-year-old Burgess Shale in British Columbia. MCZ 1811 is preserved in dorsal view and shows the overlap bewteen the digestive and nervous systems, and also well-developed eyes. You can also see this specimen in our lab's website banner! USNM 305093 is preserved in lateral view, and shows the entire central nervous system as a highly reflective carbonaceous film that runs throughout the body. Photographs by Javier Ortega-Hernández.