Fossiliferous Cambrian, Ordovician, Mississippian, and Pennsylvanian rocks, never before found in southern Mexico, have been discovered in the Nochixtlán region. Superjacent unfossiliferous sedimentary rocks may be Permian in age. Early Paleozoic and late Paleozoic intervals of marine sedimentation were bounded by intervals of positive tectonism and erosion.
The emended descriptions of the genus Amphitriscoelus and the species A. waringi Harris and Hodson are given, and a new species is proposed (A. pluriloculata). These rudist bivalves are derived from a thick Lower Cretaceous sequence of carbonate sediments interlayered with siliciclastic, volcaniclastic, and volcanic rocks in southwestern Mexico, near Huetamo, in the State of Michoacan. The species belong to a recently discovered rich fauna containing other rudists, nerineid gastropods, orbitolinid foraminifers, and calcareous algae. The fauna shows a close affinity with the Amphitriscoelus fauna of northern South America. Similar assemblages are also present in Texas, Cuba and other Mexican localities. The wide distribution of the fauna allows interpretation of paleogeographic relations among all the regions as well as interpretation of paleoecological similarities. The existence of an homogeneous large faunistic province during the Early Cretaceous is suggested.
NOMENCLATURAL NOTES Mexican Cretaceous coral species (Cnidaria, Anthozoa, Scleractinia) described as new by Filkorn & Pantoja-Alor (2009), but deemed 'unpublished' under the International Code of Zoological Nomenclature: republication of data necessary for nomenclatural
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