Stethacanthid elasmobranch remains from the Bear Gulch Limestone (Namurian E2b) of Montana. American Museum novitates ; no. 2828

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New York, N.Y. : American Museum of Natural History
"Four chondrichthyan species assigned to the cladodontid genus Stethacanthus are described from the Bear Gulch Limestone of Montana. Specimens are referred to Stethacanthus cf. S. altonensis and S. cf. S. productus. Two other species are too immature to assign with certainty to known stethacanthid spine species. The histology and morphology of three isolated cladodont tooth types is described, one of which is referred to Cladodus robustus. The species of Stethacanthidae are distinguishable on the shapes and proportions of palatoquadrate and mandible, numbers of tooth families and pectoral prearticular basals, morphology of the pelvic girdle and areas of squamation. Comparison with other Bear Gulch stethacanthids strongly suggests that the presence of specialized cranial and first dorsal fin squamation, with the presence of the first dorsal fin and spine, are secondary sexual characters of mature males. Cladoselache is indicated as the sister group of the Stethacanthidae, with the 'Symmoriidae' being the sister group of Stethacanthus altonensis"--P. [1].
24 p. : ill. ; 26 cm.
Includes bibliographical references (p. 21-24).