Conkling Cavern sits on the east side of Bishop's Cap, an outlier peak of the Organ Mountains in Dona Ana County, near Las Cruces. The cavern entrance is essentially vertical, dropping into a chamber that was originally filled with sediment to within eight feet of the opening. R.P. Conkling drew scientific attention to the site, and in the late 1920s, paleontologist Chester Stock led excavations that would uncover one of the most significant Pleistocene fossil assemblages in the American Southwest. Unfortunately, Stock never published a comprehensive study of the fauna. His premature death left the scientific community with only preliminary species lists, and the full significance of the site has been pieced together by subsequent researchers working with the original collections.

The fauna recovered from Conkling Cavern reads like a roster of Pleistocene megafauna that once roamed the Chihuahuan Desert region. Multiple species of ground sloth appear in the record, including the giant Megalonyx and the smaller Nothrotheriops. Prehistoric camels of at least two species, Hemiauchenia and the larger Camelops hesternus, left their bones in the deposits. Horses of the extinct genus Equus were present, as were four-horned pronghorns of the genus Stockoceros and the diminutive Capromeryx. Most fearsome among the predators was Arctodus, the giant short-faced bear that stood over eleven feet tall on its hind legs, alongside packs of dire wolves whose gnaw marks appear on many of the recovered bones.

Perhaps the most startling discoveries at Conkling Cavern were the fragmentary remains of two humans. One skull fragment was found at a depth of about twelve feet, close to the claw bones of a ground sloth. The second skull portion lay much deeper, approximately twenty-six feet down, buried beneath a layer of consolidated sandstone. Even more unsettling, gnawed human bones were recovered from still deeper levels in what excavators interpreted as a dire wolf denning site. Whether these individuals died in the cave, fell to their deaths through the vertical entrance, or were dragged there by predators remains unknown. Because the excavation predated modern dating techniques, the precise age of these human remains has never been determined.

The bird fauna from Conkling Cavern tells its own story of a dramatically different landscape. California condors, now restricted to reintroduction sites in the far West, once soared over southern New Mexico. Greater sage-grouse, a species now found only in sagebrush country far to the north, also appears in the record, suggesting cooler, wetter conditions during parts of the Pleistocene. Bald eagles, golden eagles, and numerous species of hawks and owls left their bones alongside those of wild turkeys, ravens, and a prehistoric subspecies of the greater roadrunner. Today the fossil collections are split between the Natural History Museum of Los Angeles County and the University of Texas at El Paso, where researchers continue to study this remarkable window into a lost world.