STREPTOGNATHODUS (CONODONTA) SUCCESSION AT THE PROPOSED CARBONIFEROUS-PERMIAN BOUNDARY STRATOTYPE SECTION, AIDARALASH CREEK, NORTHERN KAZAKHSTAN

Streptognathodus Pa elements dominate conodont faunas from the propose d Carboniferous-Permian boundary stratotype at Aidaralash Creek, north ern Kazakhstan. The phyletic development of this genus provides the me ans for subdividing the late Gzhelian to early Sakmarian prodeltaic se ction (Beds 9-37) into six zones. The preferred Global Stratotype Sect ion and Point (GSSP) for the base of the Permian System is 27 m above the base of Bed 19 at the first occurrence of Streptognathodus isolatu s Chernykh, Ritter, and Wardlaw, 1996. This arbitrarily chosen point i n the evolutionary continuum of nodose streptognathodids is recognizab le; in basinal rocks elsewhere in the Ural trough (lower part of Bed 1 6 at Usolka) as well as the cyclic shelf succession of the American Mi dcontinent (Glenrock Limestone Member of the Red Eagle Limestone). Eig ht new species of Streptognathodus occur in the Aidaralash collections : S. bellus n. sp., S. costaeflabellus n. sp., S. flexuosus n. sp., S. glenisteri n. sp., S. longilatus n. sp., S. rectangularis n. sp., S. sigmoidalis n. sp., and S. tenuialveus n. sp. In addition, three morph otypes with limited occurrence (S. sp. A-C) are left in open nomenclat ure. New collections of topotype material from the nearby Tabantal Riv er section permit clarification of S. barskovi (Kozur).