PHYLOGENETIC ANALYSIS OF THE RHODOCRINITIDAE (SUBCLASS CAMERATA, CLASS CRINOIDEA)

The Rhodocrinitidae are a diverse, long-ranging clade of crinoids that originated during the early Ordovician (Tremadocian) and persisted until the late Mississippian (Serpukhovian). The family is the largest in Order Diplobathrida (Subclass Camerata) and is composed of approximately forty-three recognized genera containing over 180 named species. Throughout their history, diplobathrids were key constituents of crinoid evolutionary faunas especially during the Ordovician when they reached their peak generic diversity.

Understanding the phylogenetic relationships of crinoids is of particular importance during the Ordovician when most crinoid clades initially originated and diversified. Although understanding the diplobathrid lineage is important for studying both the early evolution of crinoids and the role of diplobathrids in Paleozoic faunas, a comprehensive phylogenetic analysis of the Rhodocrinitidae has never been undertaken and many details of evolutionary relationships within the clade remain unresolved. This study performed a genus-level, parsimony-based phylogenetic analysis of Rhodocrinitidae using the software PAUP. The study included 43 genera with over 100 discrete morphological characters primarily collected from the type species of each genus.

This analysis is part of a larger revision of the entire Order Diplobathrida that aims to both establish the phylogenetic relationships between Rhodocrinitidae and other diplobathrid families and to revise the relationships between Diplobathrida and other crinoid clades. The recovered phylogeny will have implications for understanding early patterns of crinoid diversification during the Ordovician. It will also inform systematic revision of the Rhodocrinitidae and facilitate studies on diversity, disparity, morphology, and paleoecology within a phylogenetic framework.