Generic concepts in the Platycrinitidae Austin and Austin, 1842 (class Crinoidea)

Abstract

Platycrinitesis traditionally one of the more recognizable crinoids, a camerate crinoid with very few if any fixed brachials or interradials and a helically twisted column. Accordingly, many taxa have been assigned to this genus. With a better understanding of the Platycrinitidae, these characters actually unite the family Platycrinitidae rather than the genus. Further, use of different genus-diagnostic characters in Western Europe versus North America has resulted in a confused systematics for this important late Paleozoic family. Here, we objectively define genera within the Platycrinitidae and assign all species to either newly defined or newly named genera. A phylogenetic hypothesis, incorporating both parsimony-based character analysis and stratigraphic ranges, of the genera within the Platycrinitidae is presented.With consideration of the type species,Platycrinites laevisMiller, 1821,Platycrinitessensu stricto is distinguished fromPlatycrinitessensu lato, which is used for species that cannot be assigned with confidence to any objectively defined genus. New genera areArtaocrinusn. gen.,Collicrinusn. gen.,Elegantocrinusn. gen., andLaticrinusn. gen.; andExsulacrinusBowsher and Strimple, 1986 is designated a junior synonym ofPlatycrinitess.s.Collicrinus shumardin. gen. and sp.,Laticrinus owenin. gen. and sp., andLaticrinus wachsmuthin. gen. and sp. are described; andPlatycrinites formosus approximatus(Miller and Gurley, 1896a) is designated a junior synonym ofPlatycrinites formosus(Miller and Gurley, 1895a), which is reassigned here toCollicrinusn. gen.Platycrinitess.s. now includes 14 species and species-level taxa, and 76 species are assigned toPlatycrinitess.l. Ten species are designated nomina dubia, as are taxa based solely on columnals or pluricolumnals. Two species are designated nomina nuda, and two are transferred to genera outside of the Platycrinitidae. In addition, twenty-seven species and four open-nomenclature taxa are each reassigned to a different genus.