New early Barstovian (middle Miocene) vertebrates from the upper Torreya Formation, eastern Florida panhandle

ABSTRACT

A new vertebrate fauna has been recovered from the Dogtown Member of the Torreya Formation, Hawthorn Group (early to middle Miocene), northern Gadsden County, Florida. Fossils were recovered from four fuller's earth clay mines. This new fauna, called the Willacoochee Creek Fauna (WCF), contains at least 68 vertebrate taxa, including 29 mammals, from marine, freshwater, and terrestrial environments. The WCF is restricted to the early Barstovian land-mammal age based on the presence of Copemys, Perognathus, Rakomeryx, and Ticholeptus, and the overlapping chronologic ranges of 8 other mammals. Lanthanotherium, Perognathus, and a squalodont whale are reported from the southeastern U.S. for the first time. Biochronological range extensions into the early Barstovian are proposed for Lanthanotherium, Anchitherium clarencei and “Merychippus” primus. The WCF is the first well documented early Barstovian fauna in the southeastern U.S., thus filling a large gap in the temporal distribution of vertebrate faunas in the region. The Torreya Formation records a transition from early Hemingfordian to early Barstovian faunas. Important faunal events include the transition from parahippine to merychippine horses and their subsequent diversification, and the local first appearances of Copemys, Mylagaulus, and Perognathus. The WCF is the youngest vertebrate fauna known from the Torreya Formation and provides a new upper age limit to that unit. The occurrence of the Midway Local Fauna (late Hemingfordian) and the WCF at the same lithostratigraphic intervals indicates the Dogtown Member is time-transgressive, i.e., younger to the north.