Crinoids and stelleroids (Echinodermata) from the Broken Rib Member, Dyer Formation (Late Devonian, Famennian) of the White River Plateau, Colorado

Abstract

A crinoid and stelleroid fauna is described from the Famennian (Late Devonian) Broken Rib Member of the Dyer Formation of the White River Plateau, Colorado. The fauna postdates the Late Devonian extinction event. Six new crinoid species described, including the new genusTarassocrinus, are:Strimplecrinus dyerensis, Catactocrinus?torus, Hypselocrinus?bisonensis, Gilmocrinus?albus, Eireocrinus?coloradoensis, andTarassocrinus synchlydus.The cladid-dominated crinoid fauna is transitional between earlier Devonian and later Carboniferous faunas. It contains the first report ofCupressocrinites(a Famennian Lazarus taxon) andEireocrinus? in North America and extends ranges of several Carboniferous genera into the Late Devonian. A preliminary revision of the Rhenocrinidae is recommended. The family Glossocrinidae is recognized, and the Cupressocrinitidae are transferred to the Gasterocomacea.A new stelleroid genus and species,Pleiadeaster inceptus(Asteroidea; family unknown), and an ophiuroid,Ophiopolytretus aethus(Ophiuroidea; Lapworthuridae?) are named. In addition,Hudsonaster(Hudsonasteridae; Asteroidea) and two unassigned asteroids are present, and three further stelleroids cannot be assigned to the class level.PleiadeasterandHudsonasterare important because they suggest that the Late Devonian might have been a time of transition for asteroids.Ophiopolytretus aethusis an oegophiurid ophiuroid with distinctive respiratory? pores penetrating the disk plates.