Pleistocene high altitude amphibians and reptiles from Colorado (Alamosa local fauna; Pleistocene, Irvingtonian)

ABSTRACT

Amphibian and reptile fossils were recovered from a high-altitude (2300 meters) montarne desert in south-central Colorado. The locality spans nearly 0.2 million years during the Irvingtonian land mammal age and Nebraskan Glaciation, with three main time/climatic zones apparent from analysis of the herpetofauna. A warm and dry period preceded a cold, wet period that correlates with glacial advance down the surrounding mountains, followed by a cold and dry period after the retreat of the glacier. Ambystoma alamosensis is described as a new species of salamander related to A. tigrinum. Other salamanders show evidence of neoteny in some units.