Ammonites from the La Negra Facies (El Doctor Formation, late Albian) of the Muni Quarry, Hidalgo, central Mexico

摘要

The fossil-rich limestones (La Negra Facies of the El Doctor Formation) in the Muhi Quarry, northwestern State of Hidalgo, Mexico are of late Albian age based on the occurrence of the ammonites Mortoniceras sp., Hamites aff. renzi and ?Beudanticeras sp. Their occurrence establishes the possible presence of the M. fallax, M. rostratum, M. prinflatum, and A. briacensis Zones (upper Albian) in North America. The late Albian age of the El Doctor Formation makes its teleostean aulopiforms and acanthomorphs the oldest in the world and the occurrence of the chondrichthyans Ptychodus decurrens and Squalicorax falcatus, and the teleostean Tselfatiiformes are their oldest records in Mexico.