A review of Pleistocene vertebrate faunas from northeastern New Mexico
— Gary S. Morgan, Spencer G. Lucas, Paul L. Sealey, and Adrian P. Hunt

There are 45 known Pleistocene vertebrate localities in northeastern New Mexico. The number of Pleistocene vertebrate sites (in parentheses) in each of the northeastern New Mexico counties is as follows: Colfax (2), Union (1), Mora (2) , Harding (2), San Miguel (2), Quay (6), Torrance (10), Guadalupe (2), De Baca (6), Curry (0), and Roosevelt (12). This region comprises part of the southwestern margin of the Southern High Plains. The western portions of several of these counties do include some of the higher mountain ranges in New Mexico, but only two fossil sites are located in this mountainous region. Twenty-eight sites in northeastern New Mexico contain the mammoth Mammuthus, a genus characteristic of North American Pleistocene (Irvingtonian and Rancholabrean) faunas. There is no definitive evidence for Irvingtonian faunas in this region. Twenty-one sites in northeastern New Mexico contain Bison, the diagnostic genus of Rancholabrean faunas. Even though the other 24 sites lack Bison, most of these are probably Rancholabrean as well. Several sites have associated radiocarbon dates, clearly establishing a late Pleistocene (late Rancholabrean) age. Eight latest Pleistocene sites in this region document the association of extinct megafauna with Paleoindian artifacts, including Blackwater Draw/Clovis, Folsom, Mangano Cave, Lucy, San Jon, Stolle, Milnesand, and Ted Williamson. These localities are best known as Paleoindian archaeological sites, but we stress their vertebrate faunas.

Most of the Pleistocene vertebrate faunas from northeastern New Mexico are low diversity assemblages. Only ten of the 45 sites have three or more species of mammals. Twenty sites contain a single mammal (13 sites with Mammuthus, four with Bison, and three with Equus), and ten sites contain two mammals (six sites with Mammuthus and Equus, three with Equus and Camelops, and one with Mammuthus and Bison). The faunas are dominated by large grazing mammals, including Mammuthus, Bison, Equus, Camelops, and Paramylodon, in decreasing order of abundance. The most diverse vertebrate fauna in northeastern New Mexico is Blackwater Draw Locality 1, also called the Clovis Site, which includes more than 60 species. The mammalian fauna from Blackwater Draw (combined Gray Sand and Brown Sand Wedge local faunas, ranging from 13,000-11900 yr B. P.) consists of 39 species, including 13 members of the extinct Pleistocene megafauna. The abundance of large grazing mammals (Mammuthus, Bison, and Equus) at Blackwater Draw indicates extensive grassland or savanna habitats. A diverse fauna of small vertebrates also suggests the presence of permanent water and nearby forests. The Brown Sand Wedge fauna includes three extant small mammals now found farther north or at higher elevations (Sorer cinereus, Microtus mexicantis, and M. pennsylvanicus) and four species generally found in faunas farther south (Hesperotestudo wilsoni, Terrapene carolina putnami, Dasypus bellus, and Sigmodon hispidus). This is indicative of a late Pleistocene "disharmonius fauna" in which species co-occur that are now found in different habitats. The climatic conditions during the late Pleistocene in northeastern New Mexico, as typified by the Blackwater Draw fauna, included milder, frost-free winters, cooler summers, and more available moisture, with permanent streams, ponds, and small lakes.