New Mexico Geological Society Annual Spring Meeting — Abstracts

Prominent outcrops of the Campanian Cliff House Sandstone in the San Pablo Quadrangle near Cuba, New Mexico, include a basal sandstone that is as much as 5 m thick. Above this massive, thick-bedded sandstone is a thinner, sandy shale unit. This sandy shale contains abundant selachian teeth at NMMNH localities 5595 and 5596. The sandy shale unit ranges from 1 to 2 m thick, and is capped by another massive sandstone that is up to 10 m thick. The abundant selachian fauna is composed of Scapanorhynchus raphiodon, Squalicorax sp., Ischyriza mira, Ptychotrygon triangularis, and Pseudopyholophus mcnultyi. In New Mexico, this is the youngest Late Cretaceous selachian fauna to have this characteristic assemblage. The fauna here is slightly less diverse than the older faunas (faunas of the Dalton and Hosta sandstones, El Vado Member of the Mancos Shale, Semilla Sandstone and the Atarque Sandstone) but has the same dominant members. This selachian chronofauna arises in the Turonian, and remains very consistent through the middle Campanian. This consistent chronofauna is composed of Scapanorhynchus raphiodon, Pseudohypolophus mcnultyi, Ptychotrygon triangularis, a Squalicorax species and usually a Ptychodus and an Ischyrhiza species, depending on the facies of the localities. Squalicorax and Ptychodus are the only genera that clearly evolve and change species during this succession. The other dominant species of the chronofauna are indistinguishable from oldest to youngest.