New Mexico Geological Society Annual Spring Meeting — Abstracts

A small vertebrate fauna was collected from exposures ofthe "middle red member," Zia Formation along the Ceja del Rio Puerco, west of Rio Rancho, Sandoval County, New Mexico. This fauna includes the elephant Gomphotherium, the small protolabidine camel Michenia, a large aepycameline giraffe-camel, a small mustelid, a small canid, a small equid, and the beaver Eucastor. Co-occurrence of Gomphotherium, Michenia and Eucastor indicate a middle Miocene (late Barstovian/early Clarendonian) age for this fauna.

In addition to vertebrate fossils, several mammal trackways are also present in the Zia Formation. New Mexico Museum of Natural History locality L-2930 yields multiple trackways preserved as positives in a well-indurated, coarse-grained, cross-bedded sandstone. Tracks are preserved on multiple bedding planes. Most trackways are preserved on a single, 2m² slab. Several trackways bear didactyl prints with symmetrical, wedge-shaped hoof impressions. Manus prints are larger than the pes prints. These are referred to the ichnogenus Gambepes and can be attributed to a small camel. Two trackways consist ofdigitigrade footprints with four digits on both the manus and pes. The digital pads are subequal in size and lack claw impressions. The pes prints partly overlap the larger prints of the manus. These tracks are referred to the ichnogenus Bestiopeda. Previously, Bestiopeda have been attributed to feloids because ofthe lack of claw impressions. Nimravides, a large machairodontine felid known from early Clarendonian deposits of North America is a possible trackmaker.