56-1 Updating the Glyptocystitoidea (Rhombifera) Evolutionary History

Session: Phylogenetic and Computational Approaches in Paleobiology and Paleoecology, Part II

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Abstract:

Glyptocystitoid rhombiferans are an extinct group of marine blastozoan echinoderms. The earliest known members of the group appeared in the late Cambrian and ranged through the Devonian, achieving their peak diversity during the Ordovician. The glyptocystitoids were a widely distributed group with fossils documented from the paleocontinents Laurentia, Avalonia, Baltica, and Gondwana. Glyptocystitoids are characterized by a theca (body) covered in fairly conservative calcitic plates and pore rhomb respiratory structures, called pectinirhombs. Although pectinirhombs are a distinct feature that have been used to identify members of Glyptocystitoidea, their evolutionary history is not straightforward. As an early stem-echinoderm group, the glyptocystitoids hold critical evolutionary significance in understanding the origin and diversification of more derived groups within Blastozoa. 

Despite their evolutionary importance, a broad species-level phylogenetic estimation of the group has yet to be completed. With the discovery of new specimens of glyptocystitoids, there is a need to conduct comparative morphological analysis with respect to previously documented specimens, as well as revise the existing phylogenies. We combined previously published phylogenetic matrices of glyptocystitoids and added taxa using data derived from published literature, the Paleobiology Database, and the Global Biodiversity Information Facility. We inferred trees in both parsimony and Bayesian approaches. By doing so, we are able to provide a more robust framework of the glyptocystitoid evolutionary tree which can be used for testing future macroevolutionary hypotheses of rhombiferan echinoderms.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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