Thomas Farm Site

Mission

Thomas Farm is an ideal fossil site for combining research with education. Side-by-side, professional and amateur paleontologists have excavated vertebrate fossils at Thomas Farm for many decades, with great mutual benefit. Because the Florida Museum of Natural History owns and manages the 40-acre property that surrounds and includes the fossil site, the Museum routinely operates programs that teach people from varied backgrounds about the ancient amphibians, reptiles, birds and mammals that lived in Florida 18 million years ago. The Museum’s mission is to continue to build the world-class collections of fossils from Thomas Farm, to study and interpret these specimens and to make this knowledge readily available to scientists and the general public.

Significance

Thomas Farm is the richest Early Miocene vertebrate fossil locality in North America and perhaps the world. Since its discovery in 1931, fossils of more than 100 species have been found at the site. These species range from tiny frogs, toads, lizards, snakes, doves, cuckoos, songbirds, bats and rodents, to medium-sized species including turtles, tortoises, turkeys, hawks, foxes and badgers, and larger species such as camels, horses and rhinos. By studying these varied species, paleontologists can reconstruct the ancient animal communities of Florida as well as understand the evolutionary changes that have taken place in any given group of organisms.

Management

The fossil site and surrounding property are managed by the Florida Museum of Natural History for research and education. Florida Museum Curator of Ornithology David Steadman has managed the site since 2004, when he took over from Curator of Vertebrate Paleontology Bruce MacFadden. Steadman controls access to the site with Museum vertebrate paleontologists Richard Hulbert and Art Poyer. A couple living in a small house at the site monitors access to the property, which includes a campground, running water and full kitchen.

Location

Thomas Farm is about 8 miles north-northeast of Bell, Gilchrist County, Florida, at 29.9° N, 82.8° W. It is about 45 miles northwest of Gainesville.

Thomas Farm Map

Age

Early Miocene Epoch; Early Hemingfordian Land Mammal Age (ca. 18 million years old). The age is estimated from biochronology, which is the comparison of similar species of fossil mammals from site to site. For Thomas Farm, an Early Hemingfordian age is supported by the combined presence of the bear Phoberocyon, the mustelid Leptarctus, the rhinoceros Floridaceras, and the canid Metatomarctus. These four mammals have been found in Early Miocene fossil sites in the western U.S. that have been dated through radiometric and paleomagnetic methods.

Geology

The fossils at Thomas Farm are found in alternating beds of clay and calcareous (limestone) sand, with occasional lenses or beds of limestone gravel to boulders in a sandy matrix. Most fossils are from the various sandy layers.

Depositional Environment

The fossils are found within an ancient sinkhole and associated cave system. Fossils accumulated at Thomas Farm through “natural trap” activity (animals falling into the steep-walled sinkhole and then being unable to leave) or as the discarded prey remains of hawks and owls, or through natural mortality (especially bats that were roosting in the cave).

Excavation History and Methods

The fossil site at Thomas Farm was discovered by Clarence Simpson of the Florida Geological Survey in 1931, who found fossils on the spoil pile of a well dug by Raeford Thomas. Florida Geological Survey crews excavated at the site until January 1932. The recovered specimens were sent to famed paleontologist George G. Simpson, then of the American Museum of Natural History in New York City. Simpson recognized the fossils’ significance and quickly published the first scientific paper on the site in 1932.

Thomas Barbour of Harvard University purchased the fossil site and the surrounding 40 acres in the late 1930s and deeded it to the University of Florida, with the provision that field crews from Harvard’s Museum of Comparative Zoology (MCZ) could continue to collect fossils there. MCZ field crews led by Ted White conducted the first large scale excavations at Thomas Farm, which continued until the early 1950s. The site then was worked cooperatively until about 1960 by the MCZ and the University of Florida (spearheaded by Walter Auffenberg, Pierce Brodkorb, and Robert Bader of the UF Department of Biology; specimens curated in the Florida Museum of Natural History collection) and the Florida Geological Survey (led by Stanley Olsen, who had previously worked at Thomas Farm for the MCZ). Auffenberg and Brodkorb were the first to do extensive screen-washing at the site, which proved to have a remarkably rich fauna of small vertebrates (frogs, toads, newts, sirens, lizards, snakes, birds, bats, rodents). From 1960 to 1980, relatively little field work was done at Thomas Farm, although the Florida Museum’s paleontologists were keeping very busy at other sites.

The next major phase of excavation at Thomas Farm began in 1981, when UF graduate student Ann Pratt and co-workers established a permanent grid system and were the first to measure detailed locations and orientations for bones in the site. Many tons of sediment from the site were screen-washed to recover small vertebrate fossils. Pratt’s research led to a much-improved understanding of how the site was formed, and how animals became fossilized there.

From 1992 to 2004, Bruce MacFadden operated an annual volunteer dig at Thomas Farm known as Pony Express. This highly successful effort yielded, among other treasures, abundant exhibit-quality specimens of all three species of 3-toed horses, the very small Archaeohippus blackbergi, the medium-sized Parahippus leonensis, and the relatively large Anchitherium clarencei.

Field work at Thomas Farm has continued vigorously through the present, with at least one major field season per year. David Steadman of the Florida Museum of Natural History is currently in charge of the fossil excavations at Thomas Farm. Beginning in 2005, he has run an annual program in the springtime known as the Hummingbird Challenge. (What greater challenge could there be in the study of fossil birds than to recover the tiny bones of a hummingbird?) See details about participating in a Hummingbird Challenge.

Despite over 80 years of excavations, and the recovery of hundreds of thousands of fossils, a large volume of fossil-bearing sediment remains untouched at Thomas Farm. The good news is that we are in no hurry. Our current excavations are meticulous, using the grid system established in 1981, and removing sediment at depth intervals of only 10 centimeters (4 inches). All sandy sediment is saved and screen-washed, either on site, or at Florida Museum.

New species continue to be found and described from Thomas Farm on a regular basis. The discovery and excavation of important specimens of rare taxa also still occur routinely. For example, relatively complete skulls of the huge bear-dog Amphicyon longiramus and the small alligator Alligator olseni were found during the past several years, as well as specimens of many undescribed species of birds.

 

Source: University of Florida

http://www.flmnh.ufl.edu/index.php/thomasfarm/overview/