Places like the Hell Creek Formation in Montana and the La Brea Tar Pits in Los Angeles echo famous prehistoric discoveries. But at the bottom of a sinkhole near the small Florida town of Bell in Gilchrist County lies the richest Early Miocene vertebrate fossil locality in the world, known as Thomas Farm. Since the 1930s, researchers have pulled 18.5-million-year-old fossilized horses, bear dogs, rhinoceros and other long-extinct animals ranging from tortoises to tiny song birds from the site’s damp clay, resulting in more than 100 new species.
“Everyone thinks it’s tedious, but, you have to think, I’m the first human to ever touch this,” said Sharon Holte, a Florida Museum doctoral student studying fossil carnivores from Thomas Farm, as she slowly dusted off a bone from an extinct carnivorous mammal, possibly a canine, at the site in spring 2015.
Clarence Simpson of the Florida Geological Survey discovered the first fossils at the 40-acre Thomas Farm in 1931. Famed paleontologist George G. Simpson, then of the American Museum of Natural History in New York, recognized the fossils’ significance and published the first scientific paper on Thomas Farm in 1932. Ownership of the site passed from Harvard University to the University of Florida’s zoology department in the ‘40s, where pioneering herpetologist and conservationist Archie Carr took over its management until the Florida Museum of Natural History on the UF campus began hiring paleontologists for the first time in the early ‘50s.
“It was hot, dirty work in those days,” said Florida Museum ornithology curator David Steadman, who took over management of the site with museum paleontologists Richard Hulbert and Art Poyer in 2004. Due to the heat, humidity and mosquitos that plague North Central Florida summers, excavations typically take place from mid-October through mid-May. Dig participants camping for several days on-site endure the tropical elements, dust, mud and bugs to unearth discoveries like the skulls of a large bear dog and a dwarf alligator. The modern relatives of Thomas Farm’s fossilized animals—foxes, snakes, toads and others—roam the farm and woodland landscape, with its large, moss-draped oak trees covered with lichen.
The site has a pole barn with picnic tables, a rustic outdoor kitchen, a bathroom and a hot water heater, but these recently added amenities were not available for the site’s earlier researchers. In fact, researchers in the ‘80s filled a cow trough with water from a small on-site well to screen excavated clay for small fossils by dipping the screens in and out of the water. The Florida Museum’s earliest paleontologists recognized the importance of screening for small fossils, instead of only focusing on larger species, to develop an overall picture of the site and provide evolutionary context to the new discoveries.
“Under a microscope, it’s just like looking at big things–it’s just as exciting,” Poyer said as he examined previously screened microfossils left in the sun to dry during a spring excavation. “The cool thing about microfossils is that small animals tend to stay in one place while large animals often travel, so the small stuff serves as environmental indicators of habitat.”
At many famous sites, fossils are actually rare and one might dig for days before finding a single tooth. At Thomas Farm, however, fossils are abundant and everyone who digs finds something, making it one of the best locations for teaching paleontology in North America, Steadman said.
“When fossils are rare, you have a hard time identifying what the range of variation within a species might be,” Steadman said. “With the horses and so many other species at Thomas Farm, we can put together the whole picture, from young, adults, right through older horses, which we know were aged because their teeth were worn down. We have the advantage of looking at the entire age series of extinct species.”
A hundred years from now, Steadman says, people will still be digging and making new discoveries at Thomas Farm.
• Learn more about the Vertebrate Paleontology at the Florida Museum.