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.