Generic concepts in the Amphoracrinidae Bather, 1899 (Class Crinoidea) and evaluation of generic assignments of North American species

Abstract

The Amphoracrinidae Bather, 1899 is redefined, and all genera of this family are diagnosed with objective characters. Dilatocrinus Webster and Lane, 1987 and Pimlicocrinus Wright, 1943 are transferred into the Amphoracrinidae. Type specimens that define Displodocrinus Webster and Lane, 1987 and Dilatocrinus Webster and Lane, 1987 are clarified. The emphasis here is on genus definition, and comprehensive species-level systematics is not attempted. However, Amphoracrinus blairi Miller and Gurley, 1896a and Amphoracrinus jessieae Miller and Gurley, 1896b are designated nomina dubia; Sampsonocrinus sp. Webster and Lane, 1987 is reassigned to Amphoracrinus rupinus Webster and Lane, 1987; Amphoracrinus divergens var. multiramosus (Meek and Worthen, 1866) is reassigned to Dilatocrinus multiramosus (Meek and Worthen, 1866); and Sunwaptacrinus nevadensis Webster and Lane, 1987 is reassigned to Displodocrinus nevadensis (Webster and Lane, 1987).