New Mexico Geological Society Annual Spring Meeting — Abstracts

A diverse selachian-fossil dominated assemblage of Turonian age has been collected (and is currently being studied) near the Pipeline Road in the Ojito Wilderness area southeast of San Ysidro, Sandoval County, New Mexico. Approximately 35 kg of sediment was collected from three adjacent Western Harvester Ant (Pogonomynex occidentals, Cressen) hills, located within 100 meters of each other. The fossils are allochthonous, hydraulically concentrated. Since the fossils are collected from ant hills, the size of the fossils are also sorted by what the ants could carry. Because of the nature of the deposit, the fossils are almost all damaged.

The anthills are on clay-dominated strata of the lower Carlile Shale, but the teeth in the anthills are coming from the Semilla Sandstone that caps the cuestas that are above the valley above the anthills. Selachian teeth in the Semilla Sandstone near the anthills are of the same preservation as and in the size range of the teeth on the anthills, so we conclude the source of the anthill teeth is the Semilla Sandstone.

The vast majority of the fossils from the anthills are teeth that belong to the order Lamniformes, with three genera contributing to the bulk of the sample:Cretalamna, Scapanorhynchus, and Squalicorax. As the sorting is completed, an attempt will be made to determine which species can be assigned to each genus. The fourth most common fossil teeth belong to a batoid, Ptychotrygon. Based on the ornamentation of the ptychotrogonid fossils, more than one species of this family is likely present. Some of the rarer selachians include Chiloscyllium, Ptychodus, possible Pseudohypolophus, and an unidentified orectolobid. In addition to the selachians, at least four teleosts, several different gastropod species, inoceramid clams, and juvenile remains of one species of ammonite have also been found.