An Ice Age Behemoth: The North American Giant Ground Sloth

The giant ground sloth reconstruction on display in the Museum’s Bunting Natural History Gallery.

The Lowcountry has a rich fossil record dating back millions of years. Shifting sands and waves bury bones and teeth preserving them, so long as erosion doesn’t claim them before their discovery. Even with its gaps, the fossil record provides us with an invaluable glimpse into prehistory. From the remains we find we can learn more about the organisms that once roamed our planet and the role they occupied in their ecosystem.

Of the various time periods represented in the Lowcountry, the Great Ice Age is one of the most well represented. This time frame, formally known as the Pleistocene, looked very different in South Carolina compared to how most would imagine it. The glaciers that covered most of North America never extended far enough south to make their way here. However, the climate was significantly cooler and the ecosystems here were very different from what they are today. We interpret this from the numerous mammoth, bison, and other large bodied animal bones. Fossils of these ice mammals have been uncovered throughout the Charleston area.

Matthew Gibson and other dig crew members removing a sloth bone encased in a plaster jacket.

One of the most impressive large bodied mammals from the area is the North American giant ground sloth, Eremotherium. The largest of the ground sloths found in the Lowcountry during the Pleistocene, Eremotherium stood roughly 4.5 meters tall (almost 15 feet) and weighed over 3 metric tons. There are two known species of Eremotherium: E. eomigrans collected from Florida and E. laurillardi from the southeastern U.S. and South America. Like their modern relatives, all ground sloths were herbivores. We know this from their flat grinding teeth. These teeth would continue to grow throughout the animal’s life to make up for them continuously being ground down by chewing plant material.

A toe claw from the giant ground sloth collected from John’s Island, South Carolina.

The most imposing aspect of these sloths, aside from their great size, were their long claws. Modern tree sloths use these claws from climbing, but ground sloths were much too large to use their claws in the same fashion. There are multiple hypotheses for the use of the claws, with the most common being that the claws were used to strip branches of their leaves. Other ideas have also been thrown around based on observations of more distantly related animals as well as fossil evidence from other areas around the world.

Sloths are Xenarthrans, a group of mammals which includes armadillos and anteaters. Both of these animals also have long claws and use them primarily for digging. It’s highly likely that sloths may have used their claws for the same purpose. It has been suggested that some ground sloth species may have used their claws to dig for plant roots or even dig burrows. Massive tunnel systems in Brazil have been attributed to extinct armadillo relatives and ground sloths. We do not find those sorts of tunnels here, which either suggests they have been lost or, more likely, our sloths simply didn’t create these types of tunnels. As we learn more about ground sloths, we may even find there are other possibilities for the function of their long claws.

Ground sloth fossils are still routinely found in the Lowcountry and will likely continue to shed light on the group. Several examples of Eremotherium as well as other ground sloth species are currently on display in the Museum’s Bunting Natural History Gallery.

Matthew Gibson
Curator of Natural History