STEINHATCHEE 2A, A NEW MIDDLE PLEISTOCENE (IRVINGTONIAN) LOCALITY FROM FLORIDA

The Pleistocene vertebrate fossil record of Florida is generally regarded as excellent, with about 800 known localities producing over 200,000 tetrapod specimens, most collected from sites assigned to the late Rancholabrean (51%), late Blancan (26%), or early Irvingtonian (16%) Land Mammal Ages. Collectively the three other Pleistocene intervals, the middle and late Irvingtonian (Ir2 and Ir3, respectively), and the early Rancholabrean (Ra1), have far fewer localities and have provided only about 7% of the known tetrapod fossils from the Pleistocene of Florida. Only one site is presently dated to the Ir2 interval, and seven each to the Ir3 and Ra1. A total of 514 specimens representing ten mammalian and three reptilian taxa has been found at a new locality called Steinhatchee 2A that was discovered in 2022 in Dixie County, Florida. Like many sites in Florida, it represents an ancient sinkhole deposit. A stout-legged species of Equus comprises about 80% of the fossils at the new site and they are referred to the most common Irvingtonian horse from Florida, informally known as Equus sp. A. Specimens of the pampathere Holmesina from Steinhatchee 2A are significantly larger than H. floridanus from the Ir1 and within the size rage of H. septentrionalis from the Ir3 and Ra1. But they retain some morphologic features of the older H. floridanus. Fossils of the sloth Paramylodon harlani and the llama Hemiauchenia macrocephala, two other species that show a general trend for increasing size through the Pleistocene, are also larger than average Ir1 specimens. A palate with a nearly complete dentition of Tapirus has a unique mix of derived and primitive features that distinguish it from both Tapirus haysii (Blancan to Ir1) and Tapirus veroensis (Ir3 to Ra2). The Steinhatchee 2A assemblage is tentatively assigned to the Ir2 or, less likely, early Ir3. Further collecting, including screen-washing to recover smaller taxa, is planned, and this should increase the number of taxa and help resolve the site’s chronologic age.