Relatively few Hirnantian (Late Ordovician) crinoids are known, and none have been previously described from the palaeocontinent of Baltica. This has impaired our ability to understand patterns of extinction and biogeographic dispersal surrounding the Late Ordovician mass extinction, which triggered a major turnover in crinoid faunas. Here, we describe Tallinnicrinus toomae gen. et sp. nov., an anthracocrinid diplobathrid from the Hirnantian of northern Estonia. Tallinnicrinus is the youngest member of the Anthracocrinidae and the first...