Jurassic fishes from Black Hills of South Dakota
Scarcity of fossil Fishes in American Jura-Trias and Jura As contrasted with other countries, the American Jura-Trias contains an extraordinarily meager representation of fossil fishes. The supposed Triassic sandstones of the eastern United States yield in all but six genera and a limited number of species, the majority of which are imperfectly preserved. In none of these has the osteology of the head been satisfactorily worked out, and our knowledge of skeletal details still leaves much to be desired. The existence of piscine life in the western Trias is indicated by sparsely scattered fragments, nothing more. An even greater dearth of this class of vertebrates prevails in the American Jura, standing in marked contrast to its wealth of reptilian and mammalian remains. A few small Dipnoan teeth, described as Ceralodus guentheri Marsh* and C. robustus Knight,† are the only recognizable forms which have been discovered up to the present time.