Paper No. 9
Presentation Time: 9:00 AM-6:30 PM
REDEFINED GENERIC CONCEPTS IN THE CRINOID FAMILY ACTINOCRINITIDAE, NEW GENERIC ASSIGNMENTS OF SPECIES, AND FAMILY PHYLOGENETICS
The Actinocrinitidae was a significant contributor to the global biodiversity peak of crinoids that occurred during the Mississippian and is referred to as the “Age of Crinoids.” Although the actinocrinitids are a major component of the high diversity, they are also a source of much taxonomic confusion. Previously, generic concepts were not applied equally between Europe and North America. Genus-level diagnostic characters that were applied to European actinocrinitids have generally been applied as species-level diagnostic characters for North American actinocrinitids, creating disparity in genus definitions. To correct this problem, the global genera are defined objectively by discrete characters of the calyx and the tegmen, and the generic assignments of species are reevaluated. Unfortunately, due to this reevaluation, several well-known North American species of Actinocrinites
have been reassigned to other genera. Although inconvenient, these reassignments are necessary to recognize well-defined genus concepts to fully understand phylogeny, paleobiogeography, and evolutionary paleoecology in crinoids.
A phylogenetic hypothesis is presented for the relationships of the Actinocrinitidae genera based on a parsimony-based analysis using PAUP and plotted against stratigraphic ranges. Fifteen characters with 38 character states were used to analyze the genera. Although groupings were revealed in this analysis, the Actinocrinitidae cannot be readily divided into subfamilies and thus the subfamilies of Bowsher and Ubaghs (1978) should be abandoned. Twenty genera are described and a total of 206 species were evaluated. Among these, 55 species and one open-nomenclature taxon are reassigned to different genera, 21 species are designated as nomina dubia, and four species and one genus are now incertae sedis.