Details - Hinge grades in the evolution of crassatellacean bivalves as revealed by Permian genera

Hinge grades in the evolution of crassatellacean bivalves as revealed by Permian genera

Title

Hinge grades in the evolution of crassatellacean bivalves as revealed by Permian genera

Related Titles

Series: American Museum novitates, no. 2328

By

Boyd, Donald W.

Newell, Norman D., 1909-2005

Type

Book

Material

Published material

Publication info

New York, N.Y, American Museum of Natural History, [1968]

Notes

Title from caption.

"July 19, 1968."

Some specimens collected from the Park City Formation along Beaver Creek Canyon, in the southeastern part of the Wind River Mountains, Wyoming.

"The origin and affiliation of the conservative bivalve superfamily Crassatellacea FeМЃrussac, 1882 (= Astartacea d'Orbigny, 1844), have been uncertain. Some authors have regarded these mollusks as lucinoids. Others have placed them with the cyrenoids, or in a separate order of the Heterodonta, the 'Astartedonta.' Our discovery of numerous exceptionally well-preserved examples of the Crassatellacea of Permian age in Wyoming clarifies some problems of the early history of the group, showing how, by the acquisition of additional hinge teeth after Permian time, the hinge of living crassatellaceans became modified in separate lines from basically lucinoid to a more advanced hinge grade. Representatives of post-Paleozoic Crassatellidae and Astartidae through convergent evolution resemble one another more closely than do their Paleozoic ancestors, the new subfamilies Oriocrassatellinae and Astartellinae. Members of these Paleozoic subfamilies are sufficiently dissimilar to suggest a diphyletic origin for the Crassatellacea. The Bernard and Munier-Chalmas hinge formula and its implication of dental homologies are discussed, and a simplified, more objective hinge notation based on the Steinmann system is employed. Two new species, Oriocrassatella elongata and Astartella aueri, are described. Examples of hinge transposition of cardinal and anterior lateral teeth, but not the posterior laterals, are recorded in both. This partial transposition of hinge teeth, recorded for the first time in Paleozoic bivalves, indicates that the posterior laterals are genetically independent of the other hinge teeth"--P. [1]-2.