Oldest record of Alligator in southeastern North America

Abstract

The genus Alligator has been represented by large-bodied, predatory species in southeastern North America for at least 18 million years (early Miocene), in what is now the southeastern United States. However, the first occurrences of the genus were from a smaller-bodied species, A. prenasalis , known from South Dakota and Nebraska that are about 34 million years old (latest Eocene to earliest Oligocene). Ancestors of A. prenasalis were likewise small-bodied and are from the Great Plains. This 16 mil-lion-year-gap has left open questions regarding the arrival and body size shift of Alligator from what is now the Great Plains to southeastern North America. Recently studied fossil material from Florida exhibits the oldest occurrence of Alligator in the region (about 28–26 million years ago). A well-preserved premaxilla (UF 422816) bears the diagnostic premaxillary 'notch' of Alligator . Additional material from this and two other Oligocene sites in Florida are indicative of Alligator as well. These include well-devel-oped osteoderms, which suggest possible maturity at small body size. As of now, no records of larger Alligator from this time (or older) have been recovered from the region, possibly indicating body size may not have increased in Alligator until the Miocene