New Mexico Geological Society Annual Spring Meeting — Abstracts

Middle Turonian strata in central New Mexico cover a large range of depositional environments. The Atarque Sandstone Member of the Tres Hermanos Formation represents a shoreline deposit, that yields a diverse selachian fauna. Although Wolberg reported 22 species from the Atarque Sandstone, it only contains 11 of the species that he reported: Scapanorhynchus raphidon, Squalicorax falcatus, Ptychodus whipplei, Ptychodus anonymus, Hybodus sp., Chiloscyllium greeni, Cretodus semiplicatus, Ptychotrygon triangularis, Ischyrhiza avonicola, Pseudohypolophus mcnultyi and Rhinobatos sp. This assemblage is dominated by the teeth of the pelagic sharks Scapanorhynchus raphidon and Squalicorax falcatus, and the benthic ray Pseudohypolophus mcnultyi. The Semilla Sandstone Member of the Carlile Shale is an offshore shoal. The species present are Scapanorhynchus raphiodon, Squalicorax falcatus, Ptychodus whipplei, Ptychodus anonymus, Hybodus sp., Cretodus semiplicatus, Ptychotrygon triangularis, Ischyrhiza avonicola, Pseudohypolophus mcnultyi and Rhinobatos sp. The Juana Lopez Member of the Mancos Shale represents a deep water shoal. The species present are Ptychodus whipplei, Ptychodus anonymus, Scapanorhynchus raphiodon, Cretoxyrhina mantelli, Cretolamna sp. and Squalicorax falcatus. While up to six species may be present, the assemblage is nearly monospecific with Ptychodus whipplei being the dominant species. The abundance of Ptychodus whipplei in the deep water shoals of the Juana Lopez Memeber may indicate that Ptychodus whipplei was a deep water shark that feed at these shoals. All of the members of Rajaformes that are present in the Semilla Sandstone and the Atarque Sandstone are absent in the deeper water deposits of the Juana Lopez Member.