New Mexico Geological Society Annual Spring Meeting — Abstracts

The Cenozoic strata of New Mexico contain a sparse record of fossil mammal footprints, including sites of Eocene, Oligocene, Miocene and Pliocene age. We report the first Pleistocene record of mammal footprints, from the Tularosa basin on the White Sands Missile Range in Dona Ana County, southern New Mexico. The footprint site is at an elevation of about 1195 m on Alkali Flat (NM Museum of Natural History site L-4979), along the western shore of Pleistocene Lake Otero. The footprints were discovered in 1932 by a government trapper named Ellis Wright. Love, Hawley and Donald Wolberg examined the footprints in 1981, and identified them as belonging to elephant (mammoth) and artiodactyl (camel). Lucas, Morgan, Myers, and Pete Reser visited the tracksite in 2001 and collected metric data on representative footprints.

The fossil footprints from the Lake Otero site were made by proboscidean (mammoth) and camelid trackmakers. The tracks, preserved in convex relief, appear to be undertracks. They occur in lacustrine sediments of the Otero Formation exposed over an area of about 75,000 m². The 25 preserved mammoth tracks are very large (maximum I diameter 430-620 mm), round to ovoid in shape, and closely resemble published tracks identified as proboscidean. Two preserved mammoth trackways, one of six tracks and one of four tracks, indicate a 2-3 m stride length. A smaller heart-shaped track with two distinct digits and a pointed anterior end, photographed in 1981, is characteristically camelid. Although no such clearly-preserved tracks remain at the site, a trackway of six footprints shows the pacing gait characteristic of camelids. These tracks have diameters of 160-180 mm and a stdde length of about 1.3 m, dimensions compatible with a large camel. Teeth and postcranial bones found near the track site suggest the trackmakers were probably the Columbian mammoth (Mammuthus columbi) and a large extinct, llama-like camel (Camelops hesternus). Oriented trackways indicate these large ungulates walked to and from the waters of Lake Otero, probably to drink.