New Mexico Geological Society Annual Spring Meeting — Abstracts

The only Jurassic dinosaur footprints known from New Mexico are from the Summerville Formation. Lucas et aL (1990 NMGS Guidebook) reported two footprints of a theropod dinosaur (Grallator sp.) from Romeroville near Las Vegas in San Miguel County. They identified the track-bearing horizon as lowermost Morrison Formation, but it is actually Summerville Formation below the disconformable base (J-5 unconformity) of the Salt Wash Member of the Morrison Formation.

We document here a second theropod-dinosaur-footprint locality in the Summerville Formation of New Mexico. This locality is just west of the Chama River at Navajo Peak, Rio Arriba County at UTM 13 346460E, 4037151 N. The tracks are concave imprints in a yellowish gray to very light gray, fine-grained micaceous litharenite of the Summerville Formation about 13 m above the Todilto-Summerville contact. Fifteen tridactyl tracks are present. All are longer than wide, and some preserve claw impressions at the digit tips. These tracks are those of a large theropod and closely resemble large theropod tracks reported from European Jurassic strata.