New Mexico Geological Society Annual Spring Meeting — Abstracts

Fossil vertebrates, invertebrates and plants are locally abundant in the Petrified Forest Member (PFM) of the Chinle Formation in central Sandoval County, New Mexico. Fossils from the lower third of the PFM have been recovered from the S1/2 section 3, T15N, R1E. The majority of these fossils represent phytosaurs, including a disarticulated partial vertebral column, a toothplate of the lungfish Ceratodus dorotheae, jaw fragments, scutes and teeth. Other vertebrates include two partial interclavicles of the labyrinthodont Metoposaurus, fragmentary paramedian scutes of an aetosaur and coprolites. An isolated ungual phalanx is assigned to cf. Placerias, the first indication of this genus in New Mexico. The bennettitalean Zamites occurs with the vertebrates.

Three localities yield fossila from the upper third of the PFM: NW1/4 section 13, T16N, R1W; SE1/4 section 20, T16N, R1E; and NW1/4 section 6, T16N, R1E. The majority of fossils from these localities also represent phytosaurs, including teeth, caudal vertebrae of a dinosaur is tentatively assigned to the Ceratosauria. Freshwater bivalves are locally abundant and represent Unio arizonensis and Unio sp.

The occurrence of cf. Placerias with common metoposaur remain in the lower PFM of Sandoval County suggests correlation with the lower PFM (below Sonsels) of northwestern Arizona. The absence of metoposaurs and the presence of a small primitive theropod in the upper PFM of Sandoval County suggests correlation with the upper PFM (above Sonsela) of northwestern Arizona and the siltstone member of north-central New Mexico.