PHYLOGENETIC AND MORPHOLOGIC ANALYSES ELUCIDATE RELATIONSHIPS IN PARACRINOIDEA (ECHINODERMATA)
Within clade relationships are unclear, as describing homologous characters has proven difficult because of the high morphological disparity. To better assess potentially homologous characters, morphometric analyses are conducted prior to phylogenetic analyses to determine what characters are driving separation in morphospace. This analysis suggests respiratory structures, oral plate arrangement, and ambulacral morphology are important in separating specific subclades of paracrinoids, which is consistent with the characters that are interpreted as phylogenetically important in other blastozoan clades. Subsequent phylogenetic analysis supports these characters as clade defining. A better understanding of elemental homology within paracrinoids will further refine evolutionary relationships. Initial analyses suggest ambulacral configuration, thecal plate reduction, and structure of respiratory structures are clade defining, however, continued analyses will further elucidate the enigmatic relationships within Paracrinoidea.