Iocrinid crinoids from the Ordovician of the Baltic Region, Estonia

Abstract

A new crinoid species, Ristnacrinus oepiki sp. nov., from the Upper Ordovician (Katian Stage, Keila Regional Stage) of northern Estonia (Vasalemma) is described. The morphology and taxonomic position of the genus Ristnacrinus are discussed. Ristnacrinus previously referred to eustenocrinids based on the presence of compound radials in each of five rays is transferred to the Iocrinidae, because in a new interpretation, only one ray (C) has a superradial plate. At present, nine genera from the Early Ordovician to Early Silurian are included in the family Iocrinidae. In addition, Schaldichocrinus Rozhnov, 1997 is designated as the correct spelling of the replacement name for Pariocrinus Rozhnov, 1988 (non Eckert, 1984).