Roveacrinida (Crinoidea) from Late Triassic (early Carnian) black shales of Southwest China

Abstract

Rich material of a tiny pelagic roveacrinid from the lower member of the Carnian Xiaowa Formation, Guanling area (Guizhou Province, Southwest China), is described. The remains are assigned to a distinct species, Osteocrinus sinensis n. sp. The species is characterised by an aboral element of variable length, a radial circlet forming a small cup and unusually long arms with hollow brachials grouped in pairs. This morphology is unique among crinoids. The remains settled partly articulated on the seafloor. Coprolites comprised of roveacrinid remains and apparently produced by ammonites are common, corroborating a pelagic lifestyle of the roveacrinids. An overview of previously described species of Osteocrinus is given; the present material contributes recognising variability and growth stages of the partly insufficiently known forms.