Tarrantoceras Stephenson and Related Ammonoid Genera from Cenomanian (Upper Cretaceous) Rocks in Texas and the Western Interior of the United States: Issue 1473
William Aubrey Cobban
Jan 1988 · U.S. Government Printing Office
Ebook
30
Pages
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About this ebook
Tarrantoceras, Eucalycoceras, Pseudocalycoceras, Sumitomoceras, and Neocardioceras are closely related genera of ammonites confined to rocks of middle and late Cenomanian age. Tarrantoceras, represented by T. sellardsi (Adkins) and T. flexicostatum, n. sp., was probably derived from Calycoceras (Gentoniceras) leonense (Adkins). Eucalycoceras appeared abruptly near the end of middle Cenomanian time and then disappeared until the middle of the late Cenomanian. The genus is represented by E. templetonense, n. sp., and E. pentagonum (Jukes-Browne). Neocardioceras, which was probably derived from Tarrantoceras, is known by the new species N. uptonense and N. laevigatum of early late Cenomanian age, N. minutum, n. sp. and N. sp. of middle late Cenomanian age, and N. juddii (Barrois and de Guerne) and N. densicostatum, n. sp., of late Cenomanian age. Pseudocalycoceras and Sumitomoceras, known only from the later part of middle late Cenomanian time, were probably derived from early forms of Eucalycoceras pentagonum. Pseudocalycoceras is represented by P. angolaense (Spath), and Sumitomoceras is known from S. conlini Wright and Kennedy and S. bentonianum (Cragin).
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