Plio-Pleistocene vertebrate fossils of the El Paso Area [Vertébrés fossiles du Plio-Pléistocène de la région d’El Paso].

Résumé

Of more interest to the modern biologist are kinds of animals not now found in the immediate area. These animals give information on past climates and vegetations and, as they wax and wane through time, guide us to an understanding of how the biology of the region evolved to its present form. Particularly interesting are such animals as the Sagebrush Vole (Lemmiscus curtatus). Now approaching our area no closer than south-central Utah, this mouse is known to have extended southeast to the Carlsbad area and south to Pendejo Cave and to the bootheel of New Mexico, a few miles from the Mexican border. Closely associated with Big Sagebrush (Artemisia tridentata), the strong assumption is of a climate having similarities with that of the Great Basin, the stronghold of that plant (however, sagebrush does extend into the San Juan Basin and into northern New Mexico today). This assumption is bolstered by presence of another vertebrate closely associated with sagebrush, the Sage Grouse (Centrocercus urophasianus), at Shelter Cave and Conkling Cavern. Cooler ice-age temperatures (at least during the summer) and increased effective moisture (particularly during the winter) are indicated by a number of vertebrates. Animals and birds that reach their modern usual southern limits in northern New Mexico, but extended south in low elevations into our region during the late Wisconsinan, include the Boreal Owl (Aegolius funereus), Magpie (Pica pica), Yellow-bellied Marmot (Marmota flaviventris), Gunnison's Prairie Dog Cynomys gunnisoni), Nuttall's Cottontail (Sylvilagus nuttallii), White-tailed Jack Rabbit (Lepus townsendii), Northern Pocket Gopher (Thomomys talpoides), Bushy-tailed Packrat (Neotoma cinerea), and possibly Ermine (Mustela erminea). Also present locally in the late Wisconsinan were species that occur now in southern New Mexico, but only in montane situations high enough to support woodland or forest. Some of these kinds are the Mexican Vole (Microtus mexicanus), Merriam's Shrew (Sorex merriami), and at least two kinds of chipmunks (Tamias minimus and a larger species of Tamias).