CURIOUS BIOGEOGRAPHIC CONNECTIONS OF THE GRAY FOSSIL SITE OF TENNESSEE WITH FAUNAS OF EURASIA AND MEXICO

The early Pliocene (4.9 to 4.5 Ma) age Gray Fossil Site (GFS) of northeastern Tennessee represents the only site of its age in the Appalachian region and one of few late Neogene fossil sites in eastern North America. Among the diverse fauna and flora of the site are many taxa that persist within modern ecosystems and are known from other late Cenozoic sites. However, some GFS taxa are absent elsewhere in North America but common in Neogene and Quaternary faunas of Eurasia and Mexico. These occurrences help document previously unknown historical biogeographic connections between the eastern United States and those regions.

A major faunal dispersal event between North America and Eurasia in the late Miocene and early Pliocene is supported by some GFS mammals. The giant flying squirrel Miopetaurista occurred across Eurasia from Portugal to China, but GFS and Florida provide the only records in North America. GFS also has the only North American records of the chipmunk Eutamias, which occurs across Asia today and the Neogene of China and eastern Europe. Multiple GFS carnivorans represent lineages known from Neogene faunas in Asia, including the ailurine (Pristinailurus), meline badger (Arctomeles), and wolverine (Gulo). Moles and shrews of GFS include Parascalops, Mioscalops, Neurotrichus, a desman (Magnatalpa), Paenelimneocus, and Crusafontina, which are also known from Eurasia. Absence of GFS taxa in the fossil record of western and central North America suggests dispersals occurred via the northern United States and Canada, with evidence of the route later wiped out by Pleistocene glaciation.

Some GFS vertebrate taxa occur in Quaternary and modern faunas of North America, but are restricted to warmer, lower latitude sites. That is the case for several reptile taxa of GFS, including Alligator, beaded lizard (Heloderma), hooknose snake (Gyalopion), and tortoises (Testudinidae). The leporid Notolagus is known primarily from lower latitude sites in the southwestern United States and Mexico. Among GFS cricetids are Neotomodon and Xenomys, which are only known from late Pleistocene and modern faunas of central Mexico. GFS occurrences of these reptiles and mammals suggests they had broader early Pliocene latitudinal distributions, which likely became reduced due to late Pliocene and Pleistocene climate changes.