Scientists unearth 12,000-year-old giant sloth in Everglades restoration

South Florida Sun-Sentinel
Apr. 13, 2006

The big brown bones looked as if they had been scattered by a careless hand, strewn around a small pit about 10 feet down -- the remains of a giant sloth, frozen in time for thousands of years.

The crunching sound on April 1 signaled something more unusual than the typical rock being dug up. Contractors building a 2,000-acre filter marsh for polluted agricultural runoff in southeastern Hendry County stopped digging to see what had been unearthed: part of a massive jawbone.

The prehistoric sloth, an elephant-sized herbivore that stood taller than 20 feet on its hind legs, inhabited the Florida peninsula until roughly 12,000 years ago. Slow and lumbering, the sloth had giant claws to reach high into trees to tear down the most succulent leaves.

It was an interesting, if not rare, paleontological find buried far beneath the rich, black muck in the Everglades Agricultural Area.

"It is so well-preserved," marveled John Whitaker of Janus Research, an archaeological consultant for the South Florida Water Management District's Everglades restoration project. "I was blown away by it. I've never seen this in person."

Sloth fossils have turned up around the state, in Miami-Dade County, on the west coast and in the Panhandle. Every new discovery builds on the scientific community's knowledge of the sloth and the time in which it lived -- the Pleistocene period, from 1.8 million years ago to 11,000 years ago, the end of the last ice age.

That's also when saber-tooth cats, mastodons and mammoths -- as well as humans -- roamed the state. In the Aucilla River in the Panhandle, paleontologists have found mastodon tusks that were clearly cut off by human-made tools. There's a fossil-rich spot there known as "Sloth Hole," where many sloth remains have been found.

The Everglades sloth likely died of natural causes because there were no signs of human activity there, Whitaker said. The bones appear to be those of a young adult, said Mark Renz, a Lee County amateur paleontologist who works with the Florida Museum of Natural History in Gainesville on fossil excavations.

"Anytime you find all or part of a prehistoric animal, it's significant," Renz said as he sifted through bones large and small in plastic trays under a morning sun. "This is a nearly complete animal."

When the bones are out of the ground, they will be studied by scientists at the University of Florida in hopes of determining the age of the fossil. Possibly its teeth will reveal where it stood on the sloth evolutionary timeline. Testing the soil might reveal the age of the fossil site.

The larger bones were from the sloth, but it was not alone in death at the site. Smaller bone fragments that also were found belonged to ancient horses, deer, turtles or tortoises and camels or llamas.

The area could have been a watering hole or creek, and the animals could have died there over hundreds or thousands of years, their bones mingling. Near the top of the pit was gray sand and rock, but farther down was bluish-green clay, signifying that it once was covered with salt water, Renz said.

A freshwater stream could have emptied into the salt water, carrying animal carcasses or bones with it to be deposited in their final resting place, he said. The fossil hunters will dig around the edges of the site in the coming days to make sure they haven't missed any of the sloth bones that are there, but no full-scale, larger excavation is planned, though Renz said it's possible more remains lie below.

Eventually the area will be flooded, returning it to a more natural state, and whatever is there will remain undisturbed.