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.

墨西哥伊达尔戈州西北部 Muhi 采石场的富含化石的石灰岩（El Doctor 组的 La Negra Facies）属于晚阿尔比时代，基于菊石 Mortoniceras sp., Hamites aff. 的出现。仁子和? Beudanticeras sp. 它们的出现确定了北美可能存在M. fallax、M. rostratum、M. prinflatum和A. briacensis区（上阿尔比安）。El Doctor 组的阿尔比时代晚期使其硬骨鱼形目和棘形目成为世界上最古老的类目，并且出现了软骨鱼类 Ptychodus decurrens和Squalicorax falcatus和硬骨鱼类 Tselfatiiformes 是他们在墨西哥最古老的记录。