New Mastodont and Mammoth Remains from Pleistocene Deposits in Southeastern Arizona

ABSTRACT The remains of a mastodont and mammoth were recovered from Pleistocene deposits in southeastern Arizona. These new proboscidean remains have characteristics distinguishing them from their more typical late Pleistocene forms. The mastodont (Mammut americanum), has traits similar to those of other female mastodonts, but includes mandibular tusks. This may indicate an early Pleistocene Age or supports evidence that female mastodonts had mandibular tusks. The partial mammoth jaw and molar display characteristics similar to Mammuthus columbi, but appears to be a variant or earlier form approaching those displayed in Mammuthus meridionalis. The presence of different proboscideans with different diets, although within the same geologic unit, cannot be confirmed as being sympatric. If so, it would indicate a partitioning of resources. Mammoths are grazers, and more common in Arizona than the browsing mastodonts.