Tale of the Tennessee Rhinos

David Photo
Rhino (Teleoceras aepysoma) replica mount

In the summer of 2019, a team of paleontologists published a scientific paper announcing the exciting discovery of a new species of extinct rhinoceros! Its name is Teleoceras aepysoma, and it is found in only one place in the world: the Gray Fossil Site of East Tennessee.

A Gray Fossil Site rhino, Teleoceras aepysoma, as it may have appeared in life. The chemistry of these rhinos’ teeth suggests they ate predominantly leafy vegetation. Art by Keila Bredehoeft.

There’s a lot to admire about this new species. They’re the only fossil rhinos ever found in the state of Tennessee, they’re known from some of the most complete fossil rhino skeletons anywhere in the world, and they’re a major clue to help us understand the ecosystems of the past. But even long before the new species was identified, these rhinos have always been an important part of the story of the Gray Fossil Site. In fact, if it weren’t for the discovery of the rhinos, there might not be a Gray Fossil Site at all.

Let’s start at the beginning

Rhinos in Tennessee?

It was early in the year 2000 that a road construction crew first uncovered dark, fossil-rich sediments in the town of Gray. They called in paleontologists, who were able to recognize the remains of plants, turtles, tapirs, elephants, and more. It was clear that this site held remnants of an ancient ecosystem, but in the beginning, no one knew exactly how ancient it might be, or how important. Then, in the summer of that year, they identified rhinos.

Rhinos first appeared in North America about 50 million years ago, and the very last of them vanished from the continent around 4.5 million years ago. Before the Gray discovery, no rhinos had ever been found in Tennessee because no other sites in the state preserve fossils within that time range. In East Tennessee, most fossil sites are either much younger (late Ice Age, tens of thousands of years old) or much older (early Paleozoic Era, hundreds of millions of years old). For the Gray Fossil Site to have rhinos, along with other surprises like alligators, it must be a different age than those other sites

Rhinos were the first clue that the Gray Fossil Site must be older than 4.5 million years. We now know that the Gray Fossil Site is between 4.5-4.9 million years old.

The paleontology team realized that if the site could be saved from construction, it would be a window into a time period that had never been explored in this part of the country. The promise of scientific discovery garnered the support of Governor Don Sundquist and East Tennessee State University (ETSU). The road construction project was moved, the fossils were protected, and the site became the Gray Fossil Site.

Those first rhino fossils were only bits and pieces, but there was much more to come. In 2004, the field crew discovered the first pieces of what would turn out to be two nearly complete rhino skeletons. That part of the site is now called the Rhino Pit, and the two skeletons came to be known as Little Guy and Big Boy

The skeletons of Little Guy and Big Boy were found side-by-side in the Rhino Pit. Careful recording of the position of each bone allows the crew to create digital maps like this, showing how the skeletons were oriented in the ground.

Bigger Picture

It took years for these two rhino skeletons to be fully excavated, and then even more time for each bone to be carefully cleaned and reassembled. As these fossils made their way through the paleontological process, the picture of these ancient rhinos came into clearer focus.

The Gray Fossil Site rhinos belong to an extinct group called teleoceratine rhinos, sometimes nicknamed barrel-chested rhinos. Compared to their modern-day cousins, these ancient rhinos had short legs and round bodies. They typically had no horns, but they could fend for themselves using two large tusks on their lower jaws. Many extinct species of these rhinos have been found at fossil sites across North America, but they’re rare in the eastern part of the continent.

Early artwork of Gray Fossil Site rhinos depicted them much like other barrel-chested rhinos. This artwork has been on display at the Gray Fossil Site & Museum since 2007. Art by Karen Carr.

In the forests of ancient Tennessee, the Gray Fossil Site rhinos would have been a big deal for the local ecosystem. The chemistry of their teeth is evidence of a leafy diet, and with body weights up to two tons or more, they were some of the largest herbivores around, browsing alongside tiny tapirs and mighty mastodons. There were carnivores at the site, too, including saber-toothed cats and alligators, but a fully-grown rhino would only have had to worry about the biggest and boldest of predators.

This replica of Little Guy, the smaller of our two complete rhino skeletons, is a prominent feature in the Gray Fossil Site & Museum fossil exhibit hall. The original skeleton is incredibly complete, missing only a single toe bone!

When the Gray Fossil Site & Museum opened to the public in 2007, the biggest item on display was a replica of the entire skeleton of Little Guy. That skeleton, along with artwork depicting the rhinos as they might have looked 5 million years ago, are prominent features of the exhibit to this day.

Over the years, the remains of several more rhino specimens have been discovered at Gray. In addition to the two whole skeletons, the staff has identified bits and pieces of at least six others, including fetal remains! But ever since the early rhino discoveries, paleontologists have noticed unusual features in these rhinos. For a long time, they suspected that the Gray Fossil Site rhinos weren’t quite the same as other barrel-chested rhino species.

Rhinos Like No Others

In 2011, a graduate student named Rachel Short (now Dr. Rachel Short!) joined the paleontology graduate student program at ETSU. Her primary research subject was rhinos. During her years in the program, Rachel closely examined the fossil rhinos of Gray, and she traveled all over the United States to study rhino fossils at other museums for comparison, taking careful notes on what made the Gray Fossil Site rhinos different from all the others.

Rachel Short and the skull of Big Boy. In order to understand these rhinos, Rachel spent lots of time examining their skulls. Little Guy’s skeleton is more complete, but Big Boy has the better preserved skull.

Years after graduating, Rachel was able to revisit and finalize the rhino project to produce a full peer-reviewed scientific publication, working alongside fellow ETSU graduate Laura Emmert and ETSU professor Dr. Steven Wallace. In the summer of 2019, nineteen years after the first rhino fossils were identified at Gray, that scientific paper officially presented Teleoceras aepysoma, the Gray Fossil Site’s very own species of rhino.

With two whole skeletons to explore, Rachel and colleagues were able to describe the rhinos in great detail, with special focus on the features that make them unique. The name aepysoma means “high bodied” in reference to the fact that this species has relatively long front legs compared to other barrel-chested rhinos. This unusual feature is probably related to these rhinos’ unusual lifestyle: nearly all barrel-chested rhinos were plains-dwelling grass-eaters, but the Gray Fossil Site species ate leaves in the ancient forest.

Many questions remain about these rhinos. Little Guy and Big Boy are both adult males, so more fossils will be needed to understand how females and young might have been different. Also, these were some of the very last rhinos in North America before they went extinct, but exactly why they disappeared is also unclear.

Fortunately, more rhino fossils are found at Gray every year, and more research is sure to come. There’s a lot more to find and to learn from Teleoceras aepysoma, the Gray Fossil Site’s “high-bodied” rhinos.