Brassfield Compsocrinina (Lower Silurian crinoids) from Ohio

Abstract

Four compsocrinine camerate crinoids are described from the Lower Silurian Brassfield Formation of southwestern Ohio. These late early or early middle Llandoverian crinoids are assigned to the Periechocrinidae and include Tirocrinus trochos n. gen. and sp., Ibanocrinus petalos n. gen. and sp., Acacocrinus anebos n. sp., and the taxon Dimerocrinites? vagans Foerste, herein referred to periechocrinid incertae sedis.These Brassfield forms are the oldest known members of the Periechocrinacea and Periechocrinidae. Diagnoses of these supergeneric concepts are broadened to include the morphologic variability embodied within the Brassfield forms but not otherwise present in later periechocrinaceans.