First record of the genus Simocosmoceras Spath, 1925, Ammonitina, in Mexico. Biostratigraphic and palaeobiogeographic interpretation

Abstract

The occurrence of Simocosmoceras in Mexico is first reported from the Mazatepec area (Puebla) in East-central Mexico. Simocosmoceras pszczolkowskii apulcoensis n. subsp. shows closest morphological, resemblance with Simocosmoceras pszczolkowskii Myczynski registered in western Cuba (Myczynski 1989). Ecological adaptation to comparatively epeiric seas in eastern Mexico is interpreted to cause phenotypic deviation with respect to Simocosmoceras pszczolkowskii Myczynski reported from western Cuba. The lack of transient phenotypes between Mexican and Cuban Simocosmoceras is assumed to support the interpretation of Simocosmoceras pszczolkowskii apulcoensis n. subsp. as a geographic subspecies. The new subspecies is interpreted to indicate stratigraphic horizons within the Semiforme/Verruciferm Zone in the Mediterranean Tethys.