The Chico Springs locality, Nacimiento Formation, San Juan Basin
— Thomas E. Williamson and Spencer G. Lucas

The Chico Springs locality (= "Gallegos Canyon" and "AMNH locality I") is one of David Baldwin's fossil vertebrate collecting localities from the 1880s. Many holotypes and important early Paleocene (Torrejonian) mammals named and described by E. D. Cope are from this 1+ cality, as are numerous additional specimens collected by early expeditions from the American Museum of Natural History. The precise location of this important collecting area until recently has been lost. W, relocated this area in 1991 by using unpublished field notes of W. J. Sinclair (1913), and collected numerous additional specimens there that represent Catopsalis fissidens, Psittacotherium multifragum, Triisodon crassicuspis, Mimotricentes subtrigonus, Promioclaenus lemuroides, Protoselene opisthacus, Tetraclaenodon puercensis, Anisonchus sectorius, Haploconus angustus, Periptychus carinidens, and Deltatherium fundaminus. Additional topotype remains of the large taeniolabidid multituberculate Catopsalis fissidens we particularly significant, as it is an extremely rare taxon. Additional remains of the rare triisodontid Triisod n crassicuspis include the first identified parts of the upper dentition. The lower Torrejonian fossil localities of the Nacimiento Formation, San Juan Basin, New Mexico, and throughout western North America are generally poorly sampled. The Chico Springs section can be correlated using lithostratigraphy to sections in both De-na-zin Arroyo and in Kutz Canyon and is shown to be from near the base of the stratigraphic interval that yields Torrejonian mammals. These strata are within the reversed polarity zone correlated with Chron 27R and correlate, in part, with the "Dragonian" fauna of Dragon Canyon, Utah.