WITHLACOOCHEE RIVER 1A
University of Florida Vertebrate Fossil Locality MR060
Location: In channel of Withlacoochee River about 10 miles southeast of Dunnellon, Marion County, Florida; 29.0° N, 82.3° W.
Age: early Pleistocene Epoch; later half of Blancan Land Mammal Age. About 1.9 to 2.2 million years old (Hulbert, 2010).
Basis of Age: vertebrate biochronology (presence of Megalonyx leptostomus, Sigmodon medius, Nannippus peninsulatus, and Hemiachenia gracilis, species only known from late Blancan localities in Florida).
Geology: fossils derive from a sandy gray clay filling shallow depressions and crevises in an irregular limestone surface.
Depositional Environment: clay probably represents the remnants of material filling an ancient sinkhole.
Excavation History and Methods: Discovered by Aaron Gipson in 1995. Collected by A. Gipson, D. Gibson, and friends and relatives between 1995 and 2012 (collecting still on-going as water conditions permit). Specimens donated to the Florida Museum of Natural History. Additional collecting by A. Gipson, D. Gibson, and Florida Museum of Natural History field crews in the spring of 2009 and 2011, including large samples of matrix for screenwashing (diver in Figure 1 is collecting in situ clay from a limestone depression). About 2,000 cataloged specimens in the Florida Museum of Natural History collection.
Figure 1. UF grad student Alex Hastings collecting in situ fossiliferous sediment at the Withlacoochee River 1A site in 2009.
Comments: The only known Florida locality with both Paramylodon harlani and Nannippus peninsulatus. Therefore, one of the youngest, if not the youngest, record of three-toed horses in North America. The fossils are found along about a 30-yard-long stretch of the river at a depth of two to six feet (1-2 meters). Freshwater species are relatively rare; small tortoise shell elements and armadillo osteoderms both very common. Although primarily represented by postcranial skeletal elements, mammalian carnivores are remarkably diverse at Withlacoochhee River 1A (nine species, see faunal list below). Most of this important fauna has not yet been studied.
Figure 2. Withlacoochee River 1A locality.
Hulbert Jr., R. C. 2010. A new early Pleistocene tapir (Mammalia: Perissodactyla) from Florida, with a review of Blancan tapirs from the state. Bulletin of the Florida Museum of Natural History 49(3):67–126. http://www.flmnh.ufl.edu/bulletin/vol49no3/vol49no3.pdf
Faunal List (†=extinct species; *=species no longer living in Florida)
Rana sp., probably Rana capito
†Bufo cf. defensor Siren sp.
Lampropeltinae and/or Colubrinae (likely > 1 sp.)
†Hesperotestudo (Hesperotestudo) mlynarskii
†Hesperotestudo (Caudochelys) n. sp.
Alligator sp., near Alligator mississippiensis
Canis sp., probably †Canis lepophagus
Mustela sp., cf. M. frenata
Soricidae, cf. Cryptotis sp.
†Aztlanolagus n. sp.
cf. Mammut sp.
Author: Richard C. Hulbert Jr.; Original Date: January 30, 2009
Last Edited by: Richard C. Hulbert Jr.; Last up-dated On: March 29, 2013