Mississippian–Permian evolution and paleogeographic distribution of the Cromyocrinidae and Pirasocrinidae (Crinoidea, Dendrocrinida)

Late Paleozoic macroevolutionary crinoid faunas were dominated by dendrocrinids, replacing most of the camerata crinoids that had dominated the Early and Middle Paleozoic macroevolutionary crinoid faunas. Two dendrocrinid taxa, the Cromyocrinidae and Pirasocrinidae, first recognized in the Mississippian (Viséan), attained their greatest generic diversity in the late Moscovian to early Kasimovian, declined in the Late Pennsylvanian and Early Permian, and became extinct in the Late Permian or end-Permian extinction event. The paleontologic record of the Cromyocrinindae and Pirasocrinidae is best documented from the Midcontinent of the United States and both are recognized worldwide in the Late Paleozoic. Their diversity in the latest Pennsylvanian and Early Permian is probably greater than currently recognized because disarticulated ossicles that are ascribed to one or the other of the two families in described faunas are commonly not recognizable at the genus level. Both families show individual evolutionary trends while following the general evolutionary trends of the dendrocrinids.