Late Hemphillian (Late Miocene) vertebrate fauna from the Black Mesa Quarry, Chamita Formation, Rio Arriba County, New Mexico
— Gary S. Morgan, Daniel J. Koning, and Spencer G. Lucas

The Black Mesa Quarry contains a newly discovered vertebrate fauna of late Miocene (late Hemphillian) age from the Chamita Formation near Lyden, Rio Arriba County, northern New Mexico. This fauna is derived from the Cuarteles Member stratigraphically high in the Chamita Formation. The site is only 10-16 m below the overlying Pliocene Servilleta Basalt and is in a relatively intact landslide block on the eastern slope of Black Mesa. Eight taxa of mammals are currently known from the Black Mesa Quarry: the puma-sized cat Pseudaelurus cf. P. hibbardi, the one-toed horse Dinohippus interpolatus, the giant camel Megatylopus cf. M. matthewi, the llama-like camel Hemiauchenia cf. H. vera, an unidentified antilocaprid, the rabbit Hypolagus cf. H. gidleyi, a smaller unidentified rabbit, and a small unidentified murid rodent. Further work at the Black Mesa Quarry, together with additional screenwashing for microvertebrates, will certainly add to the faunal list. The Black Mesa mammals, in particular D. interpolatus, M. matthewi, and H. gidleyi, are similar to the well known late Hemphillian faunas from the San Juan Quarry and Rak Camel Quarries. These other quarries also occur in the Chamita Formation about 7 km to the southwest. Several ⁴⁰Ar/³⁹Ar radioisotopic dates on tephras indicate that the San Juan Quarry and Rak Camel Quarries are between 6.8 and 7.0 Ma. The Black Mesa fauna is either time-equivalent to or somewhat younger than the San Juan Quarry fauna and Rak Camel Quarries fauna (5.9-6.8 Ma), but is older than latest Hemphillian (~5 Ma) faunas such as Walnut Canyon in southwestern New Mexico.