Journal Article

Devonian cladid crinoids: families Glossocrinidae Goldring, 1923, and Rutkowskicrinidae new family

McIntosh, G C

2001

Overview

The cladid crinoid order Poteriocrinida Jaekel, 1918 is a polyphyletic group that includes a variety of independent lineages united solely by the presence of ramulate or pinnulate arms. One of these lineages is the Rutkowskicrinidae new family herein assigned to the order Dendrocrinida. Bather 1899. Genera assigned to this new family include Rutkowskicrinus new genus, Decorocrinus new genus, Iteacrinus, Nassoviocrinus, Quantoxocrinus, Sacrinus, Sostronocrinus, ?Propoteriocrinus, and ?Schmidtocrinus. Members of this family are characterized by low conical cups with ridged thecal plates. U-shaped peneplenary radial facets bearing faint transverse ridges, a proximal median ridge on the posterior side of a long, narrow, predominantly straight anal sac, and pentagonal columns with one to two cirri per nodal. Arms in this family are highly variable, ranging from isotomous to heterotomous and pinnulate. The arms in the type specimen of Rutkowskicrinus patriciae n. sp. preserve all these various arm stages. The oldest presently known rutkowskicrinids occur in the Late Silurian (Ludlovian) of Australia and the Early Devonian (Pragian) of western Europe. The family diversified during the Middle Devonian (Givetian) in northeastern North America, and declined in numbers and diversity throughout the Late Devonian before going extinct in the Early Mississippian (Tournaisian). The Glossocrinidae Goldring, 1923, containing Glossocrinus, Charientocrinus, Catactocrinus, and Liparocrinus, is also reviewed. This family, distinguished by a strongly recumbent anal sac in the B-E plane and a prominent median ridge extending the entire length of the anal sac, was derived from the Rutkowskicrinidae during the Middle Devonian (Givetian) and diversified in the Late Devonian before going extinct at the Frasnian-Famennian boundary. The previously described rutkowskicrinid and glossocrinid genera listed above were assigned by Moore et al. (1978) to the dendrocrinid family Mastigocrinidae and poteriocrinid families Rhenocrinidae, Poteriocrinitidae, and Scytalocrinidae. Studied taxa include Rutkowskicrinus patriciae new genus and species, Rutkowskicrinus collieri new genus and species, Nassoviocrinus costatus new combination, Nassoviocrinus schultzei new combination, Nassoviocrinus? duluki new combination, Nassoviocrinus? ornatus new combination, Nassoviocrinus? chilmanae new species, Decorocrinus arkonensis new combination, Decorocrinus cooperi new combination, Quantoxocrinus clarkei new combination, Glossocrinus halli new combination, and Charientocrinus bellitubatus new combination.

• Subject: Crinoidea