Collicrinus excavatus (Hall, 1861), generic affinity for a Lower Mississippian crinoid (Phylum Echinodermata)

Platycrinites was long a “catch-all” genus that was loosely defined in North America. Ausich and Kammer (2009) rectified the inconsistencies of generic diagnoses to define the Platycrinitidae better; however, due to preservation, many species were not known from specimens with sufficient characters to be placed confidently into a genus and, thus, were designated Platycrinites sensu lato. Collicrinus excavates (n. comb.) was one such species. A specimen with a complete theca and partial arms preserved was discovered in southwestern Missouri in the Burlington–Keokuk Limestone. With the discovery of this specimen, C. excavatus has been fully described and placed in the correct genus. Further, the associated fauna of new C. excavatus specimens, reported here, helps to evaluate the stratigraphic position of this species, which is now considered to be only from Burlington Pelmatozoan Association I and II, roughly equivalent to the Dolbee Creek and Haight Creek Members of the Burlington Limestone.