Fossil pigmy rattlesnake inside the mandible of an American mastodon and use of fossil reptiles for the paleoclimatic reconstruction of a Pleistocene locality in Puebla, Mexico

Abstract Records of Pleistocene reptiles are relatively well known in different countries. However, reptile fossil records of Pleistocene from Latin America are scarce and limited to presence data associated with records of megafauna remains. Taphonomic studies in Pleistocene reptiles are focused on finding out the origin of the paleontological remains; that is, if the remains found at a particular place correspond to organisms that lived and died there or if they were carried out and deposited there by water currents or predators. Pleistocene reptiles have been used as a proxy for qualitative paleoclimatic reconstructions of localities. In this study, we describe the fossil record of squamate reptiles from the Pleistocene of San Jose Buenavista (Puebla, Mexico), and the taphonomic relationship between them and the associated megafauna, as well as reconstruct the paleoclimate of the paleontological site in Central Mexico where the remains were found. We present the first Mexican Pleistocene record of Anolis and Storeria, the third fossil record of the alligator lizard Barisia sp. in Mexico, and the first North American Pleistocene record for the rattlesnake Crotalus triseriatus. The rattlesnake (C. triseriatus) was found inside the mandible of the American mastodon (Mammut americanum). This finding suggests that the mastodon remains were used as burrow by the rattlesnake during the Pleistocene. Paleoclimate was reconstructed using the Mutual Ecogeographic Range method, which uses the distribution and climate niche of the nearest extant representatives of the identified fossil taxa. A mean annual temperature of 13.91 ± 1.54 °C and an annual precipitation of 964.04 ± 316.82 mm were inferred for the locality. This suggests that the assemblage of fossil species found inhabited the locality during a glacial period.