Late last month, the Tampa Bay Fossil Club announced its findings from a 2022 excavation in Florida’s Big Bend region. A total of 552 fossils from the ice age were unearthed and identified.
The dig site is located near fossil collector Robert Sinibaldi’s property on the Steinhachee River. The fossil club hopes to discover fossils that help to “unravel mysteries of Florida’s Ice Age,” according to a statement from the organization’s Michael and Seina Searle.
Sinibaldi and fellow collector Joseph Branin’s discovery of fossilized horse, armadillo, and tapir remains is significant due to the time period from which they are believed to have come from.
Paleontologists from the Florida Museum of Natural History determined that the assortment of fossils was ultimately preserved during the middle Irvingtonian period of the Pleistocene Ice Ages, the email added.
The scientists theorized that this process took place approximately half a million years ago when these animals fell into the sinkhole. With the passage of time, the sinkhole filled in with sediment. This, in turn, preserved remains from a notably difficult time period from which to find fossils.
“The fossil record everywhere, not just in Florida, is lacking the interval that the site is from – the middle Irvingtonian North American land mammal age,” said Rachel Narducci, vertebrate paleontology collections manager at the Florida Museum.
So how did the pair come upon the find? As they had already been diving at the site for years, the lack of results, combined with low visibility, was becoming disheartening.
The high concentration of tannins in the water made it incredibly tough to see much at all. Sinibaldi likened the experience to “diving in coffee.” As they prepared to leave the site following another excavation attempt in June of 2022, Branin “looked down and happened to see horse teeth,” the statement continued.
What followed was a flurry of discoveries of fossils in “pristine condition,” including:
• Horse teeth
• A hoof core
• A tapir skull
• Ankle and foot bones
At the time, the duo knew it was an important discovery, but they did not know just how significant it was. Prior to their findings, there was only one other site in the entire state, which is believed to have come from this time period.
“An evolutionary transition without a fossil record,” the February email called it. The significance here is that the eras just before and after this period have seen the appearance, extinction, or notable change of several species, but the middle Irvingtonian has seen very little.
The now-extinct genus Holmesina, which looked similar to a large armadillo, was found. The species Holmesina floridanus is believed to have first appeared in Florida averaging 150 pounds in size. Eventually, as the original species grew over time, the 475-pound Holmesina septentrionalis emerged.
Narducci called it “essentially the same animal” but noted that “through time, it got so much bigger, and the bones changed enough that researchers published it as a different species.”
“This gave us more clues into the fact that the anatomy kind of trailed behind the size increase. So, they got bigger before the shape of their bones changed,” Narducci explained. Only later, it seems, would the animals evolve skeletal features to help support the heavier body weight.
Seventy-five percent of the discovered fossils were identified to have come from “an early subgroup of living horses that includes the domestic horse and its wild relatives known as the caballines.” Due to the wear on the recovered teeth and prior knowledge of the environments that horses tend to frequent, this dig allowed paleontologists to glean clues on the diets and habitat of these ancient animals.
Discoveries like these offer glimpses into the lives and growth of these species during a little-studied period of the prehistoric record. While the excavation of such a location will likely yield results slower than desired, those involved are “hopeful” that there are more fossils yet to be discovered.
The Tampa Bay Fossil Club will present the 38th annual Fossil Fest on March 15 and 16 at the Florida State Fairgrounds.
“Our goal is to teach Floridians about the prehistoric creatures and people that were here long before us,” says club president Mike Searle. “You don’t have to travel to far-away exotic places to find these fossils. Mammoths, wolves, camels, and rhinos lived right here where we live today. Their fossilized remains are everywhere in Florida”, says Searle. Learn more at www.tampabayfossilclub.com
