Cenozoic vertebrates from Socorro County, central New Mexico
— Gary S. Morgan, Spencer G. Lucas, and David W. Love

The Cenozoic vertebrate record from Socorro County in central New Mexico consists of 20 faunas ranging in age from Eocene through Pleistocene. The Carthage Local Fauna (LF) of middle Eocene age (Bridgerian North American landmammal “age”—NALMA) is the oldest of these faunas. The presence of the brontothere Telmatherium restricts the age of the Carthage LF to late Bridgerian (Twinbuttean, 46-46.5 Ma). The two other Paleogene vertebrate sites in Socorro County are both ichnofaunas, including three trackways of Eocene artiodactyls from the Baca Formation in the Gallinas Mountains and two artiodactyl tracks from Oligocene volcaniclastic sediments in the San Mateo Mountains. Despite the widespread occurrence of Miocene rocks of the Popotosa Formation in Socorro County, the only fossil so far reported from this unit is a complete skull, lower jaws, and partial skeleton of the oreodont Merychyus major from a late Miocene (late Clarendonian NALMA) site on the Bosque del Apache National Wildlife Refuge near San Antonio. Pliocene (Blancan NALMA) sites from the Ceja and Palomas formations in the Rio Grande valley include Abeytas, Arroyo de la Parida, Sevilleta, Silver Canyon, and Veguita. The best known of these is the Arroyo de la Parida LF with 14 species of vertebrates, including the gomphothere Rhynchotherium tlascalae, indicating an late early Blancan age (~3 Ma). Pleistocene sites are distributed throughout the county, including: Lake San Agustín, VLA, and White Lake from the Plains of San Agustín in northwestern Socorro County; Lemitar, San Antonio, and Socorro from the Rio Grande valley; and Chupadera Arroyo and Mockingbird Gap from the eastern portion of the county.