Parallel evolution in early trigoniacean bivalves. Bulletin of the AMNH ; v. 154, article 2

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New York : American Museum of Natural History
"The present work is a morphologic-taxonomic revision and inquiry into the evolution of geologically ancient (late Paleozoic and Triassic) marine bivalves of a formerly cosmopolitan superfamily Trigoniacea that are represented today by a single Australian genus Neotrigonia. Trigoniaceans, after a very long period of extreme conservatism, underwent a notable radiation in the Jurassic and Cretaceous periods, then nearly became extinct immediately afterward. Particular attention is devoted here to stratigraphic-morphologic analysis from which it is concluded that the complex hinge of the younger genera probably is of diverse origin as apparently it was attained after divergence of separate lines. Each line is characterized by chronological propinquity of relatively stable surface markings and external form. The modified taxonomic arrangement adopted here recognizes the polyphyletic attainment of the derived hinge characters shared in common by the most advanced genera of trigoniaceans. It results in improved resolution of phylogenetic and biostratigraphic problems as contrasted with the more generalized conventional 'horizontal' scheme of classification. Much of the memoir reports our original observations on morphologic details and anatomy of living and fossil trigoniaceans from Australia, Europe, and America and attempts a taxonomic revision of 27 North American Upper Carboniferous and Permian species. New families introduced here are the: Eoschizodidae, Eoastartidae, and Costatoriidae. The following genera are given more than perfunctory attention: Devonian only: Eoschizodus, Rhenania, Hefteria; Devonian to Permian: Schizodus; Permian only: Heteroschizodus, new genus, Lyroschizodus, new genus, Procostatoria, new genus, Paraschizodus, new genus, Scaphellina, Eoastarte, and Kaibabella; both Permian and Triassic: Neoschizodus and Costatoria; Triassic only: Heminajas, Pachycardia, Trigonodus, Gruenewaldia, Lyriomyophoria, and Costatoria"--P. 57.
p. 55-162 : ill. ; 26 cm.
Includes bibliographical references (p. 158-162).