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

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.

Automated summary

The fossil-rich limestones in the Muhi Quarry of northwestern State of Hidalgo, Mexico are dated to the late Albian age and suggest the presence of various zones in North America. The El Doctor Formation contains the oldest teleostean aulopiforms and acanthomorphs in the world, with the oldest records of chondrichthyans and teleostean Tselfatiiformes in Mexico.