Pleistocene vertebrates from the White Sands Missile Range, southern New Mexico
— Gary S. Morgan and Spencer G. Lucas

We report 12 species of vertebrates from 14 late Pleistocene (Rancholabrean) fossil sites on the White Sands Missile Range (WSMR) in southern New Mexico. Twelve of these sites, named the Lake Otero Fauna, occur in the Tularosa Basin near Alkali Flat in Dona Ana County and Alkali Spring in Sierra County and are associated with Pleistocene Lake Otero. The fossils are derived from the Otero Formation, which is predominantly composed of fine-grained gypsiferous sediments of lacustrine origin, with several thin beds high in the unit consisting of coarse volcaniclastic sands and gravels of fluvial or deltaic origin. New Mexico Museum of Natural History (NMMNH) site L-4979 consists mostly of large footprints of a proboscidean, presumably the mammoth Mammuthus, and smaller footprints of a camel. A green gypsiferous clay (L 4980) about 2 m higher in the section has produced several partial teeth of the horse Equus and nine species of small vertebrates: the frog Rana, a colubrid snake, a lizard, a small bird, the rabbit Sylvilagus cf. S. auduboni, a squirrel (Sciuridae), the mouse Peromyscus, the muskrat Ondatra cf. O. zibethicus, and the vole Micmtus. Nine sites south of Alkali Spring have produced teeth and postcranial elements of Mammuthus, Equus, and the large camelid Camelops. Most of the horse fossils and a single complete camel scapula were derived from coarse-grained sediments in the Otero Formation, whereas several partial Mammothus teeth were found in gypsiferous clays. A partial mammoth skeleton was discovered in 1934 near Davies Tank at the southern end of WSMR, and two teeth of Camelops were collected in 1930 in the vicinity of Mockingbird Gap in the northern portion of WSMR. We also discuss seven Pleistocene sites located just outside the boundary of WSMR. Two sites near Keen Spring east of the WSMR boundary in the Tularosa Basin in Lincoln County have produced Mammuthus columbi and the kangaroo rat Dipodomys. Five sites in Chupadera Arroyo north of the WSMR in the Jomada del Muerto Basin in Socorro County have produced teeth and tusk fragments of Mammuthus. One of the Chupadera Arroyo mammoth localities, the Mockingbird Gap Site, may be associated with a Paleoindian archaeological site.

The occurrence of Microtus in the Lake Otero Fauna is indicative of mesic forested habitats, whereas the frog and muskrat suggest the presence of permanent water in the Tularosa Basin during the late Pleistocene. The large grazing ungulates, including horse, camel, and mammoth, would have required extensive grasslands, as well as a permanent source of freshwater. The diverse sample of freshwater mollusks and extensive lake sediments of the Otero Formation further support the presence of Lake Otero in the Tularosa Basin during the late Pleistocene. The Lake Otero Fauna and two other vertebrate faunas from New Mexico associated with Pleistocene lakes, the Lake Estancia Fauna from Torrance County and the Lake San Agustin Fauna from Socorro and Catron counties, have many similarities, including the presence of numerous aquatic vertebrates and species that now occur farther north or at higher elevations, as well as abundant molluscan faunas. The Lake Otero Fauna provides additional evidence for cooler and wetter climatic conditions in New Mexico during the late Pleistocene.