George C. McIntosh

DEVONIAN CLADID CRINOIDS: FAMILIES GLOSSOCRINIDAE GOLDRING, 1923, AND RUTKOWSKICRINIDAE NEW FAMILY

Abstract 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 (Goldring, 1954) new combination, Nassoviocrinus schultzei (Haarmann, 1921) new combination, Nassoviocrinus? duluki (Kesling, 1969) new combination, Nassoviocrinus? ornatus (Goldring, 1954) new combination, Nassoviocrinus? chilmanae new species, Decorocrinus arkonensis (Goldring, 1950) new combination, Decorocrinus cooperi (Goldring, 1926) new combination, Quantoxocrinus clarkei (Williams, 1882) new combination, Glossocrinus halli (Goldring, 1923) new combination, and Charientocrinus bellitubatus (Kesling, 1973) new combination.

Natural selection shaped the rise and fall of passenger pigeon genomic diversity

Genetics of the passenger pigeon The now-extinct passenger pigeon used to be one of the most numerous vertebrates on Earth. Murray et al. examined the genomes of four passenger pigeon samples from different locales within its range. They describe the interplay between passenger pigeon population size, genome structure and recombination, and natural selection. They conclude that a reduction in genetic diversity provided few avenues for the bird to respond to human pressures, which ultimately drove it to extinction. Science, this issue p. 951 The passenger pigeon’s genome exhibits the hallmark of natural selection dominating genome-wide evolution. The extinct passenger pigeon was once the most abundant bird in North America, and possibly the world. Although theory predicts that large populations will be more genetically diverse, passenger pigeon genetic diversity was surprisingly low. To investigate this disconnect, we analyzed 41 mitochondrial and 4 nuclear genomes from passenger pigeons and 2 genomes from band-tailed pigeons, which are passenger pigeons’ closest living relatives. Passenger pigeons’ large population size appears to have allowed for faster adaptive evolution and removal of harmful mutations, driving a huge loss in their neutral genetic diversity. These results demonstrate the effect that selection can have on a vertebrate genome and contradict results that suggested that population instability contributed to this species’s surprisingly rapid extinction.

Review of the Devonian camerate crinoid Bogotacrinus scheibei Schmidt from Colombia

Two recently collected specimens of Bogotacrinus scheibei Schmidt, 1937, from the Devonian (Emsian-Eifelian) Floresta Formation of Colombia reveal that Bogotacrinus is a dicyclic camerate crinoid genus closely related to Pterinocrinus Goldring, 1923 (Lower-Upper Devonian of eastern North America and western Europe), and Ampurocrinus McIntosh, 1981 (Lower De- vonian of Bolivia). The new diplobathrid camerate crinoid family Pterinocrinidae, characterized by species with low conical dicyclic cups and rami composed of compound, bipinnulate brachials, is herein proposed to accommodate these three genera. This family originated in western Europe and migrated into the Malvinokaffric and southern Eastern Americas Realms during the Early Devonian and into the northeastern Appalachian Basin by the Late Devonian.