Vertebrate biostratigraphy of the Eocene Galisteo Formation, north-central New Mexico
— Spencer G. Lucas and Barry S. Kues

Prior to the initiation of the rifting that formed the Rio Grande trough, a broad inland basin existed in north-central New Mexico. During the early Tertiary, from 300 to 1,200 meters of fluvial sandstone, conglomerate, mudstone and freshwater limestone of what is now referred to as the Galisteo Formation were deposited in this basin (Gorham and Ingersoll, this guidebook). The age assigned to these continental sediments has varied; structural and lithologic considerations have resulted in age determinations ranging from Cretaceous to Oligocene. However, new vertebrate biostratigraphic evidence presented here confirms age assignments initially determined by Stearns (1943) and Robinson (1957); the Galisteo Formation ranges in age from early to late Eocene. In this paper, we briefly review previous biostratigraphic work and add to it the preliminary results of our ongoing research on the Galisteo Formation. The following institutional abbreviations are used: AMNH = American Museum of Natural History, New York; MCZ = Museum of Comparative Zoology, Harvard University, Cambridge; UCMP = University of California Museum of Paleontology, Berkeley; UCOM = University of Colorado Museum, Boulder; UNM-GE = University of New Mexico, Department of Geology Eocene Galisteo Collection, Albuquerque.