The new species is a member of a group called the barrel-chested rhinos, which were once widespread across the plains of North America. They were typically grass-eaters, and they looked sort of like hippos, with short legs, round bodies and a nose adorned with only a very small horn or no horn at all. But the Gray Fossil Site rhino discovered by East Tennessee State University paleontologists is very different.
“If you put it in a group of other Teleoceras species, it would be like the NBA player. It would be noticeably taller and larger,” says Rachel Short, lead author of the new paper and a 2013 graduate of the ETSU master’s degree program in paleontology. One of the major distinguishing features of the new species is its long front limbs, which gave it a height boost not seen in its cousins. In fact, the name aepysoma means “high-bodied.”
This “high-bodied” rhino was also living an unexpected lifestyle compared to its relatives. The ancient habitat of the Gray Fossil Site was not a grassy plain, but a dense forest, and previous chemical analysis of this rhino’s teeth has shown that it was browsing on leaves, not grazing on grass.
Short, currently a Ph.D. candidate at Texas A&M University, suspects it is no coincidence that this unusually shaped rhino was living in an unusual place. The extra height of T. aepysoma may have been a helpful adaptation while it competed for leafy greens with smaller herbivores like tapirs.
The detailed description of this new species was possible thanks to the quality of preservation at the Gray Fossil Site. While most extinct species are known only from fragmentary remains, T. aepysoma is represented by two practically complete skeletons, affectionately named Little Guy and Big Boy, as well as partial remains of at least four others. Little Guy, who is identified in this paper as the reference specimen or holotype for the species, has every single bone in the body except for one missing toe bone.
This fossil bounty allowed the researchers to present what they describe in their study as “a detailed, thorough, bone-by-bone description” of the rhino.
“I feel like this is practically going to be a rhinoceros reference manual,” says Laura Emmert, study coauthor and field and lab technician at the Gray Fossil Site. Like Short, Emmert also graduated from ETSU in 2013 with a master’s degree paleontology.
Partial rhino remains were first found at the Gray Fossil Site in 2000, and from 2004 to 2006, paleontologists discovered and excavated the full skeletons of Little Guy and Big Boy.
“It was almost immediately that we started noticing these weird differences, especially in the legs,” says Dr. Steven Wallace, study co-author and professor of paleontology in the ETSU Department of Geosciences. “Once we got the skull together, we noticed the skull was weird, too.”
But it wasn’t until Short started her master’s research in 2011 that the rhinos finally got the academic attention they were waiting for. Then it was a matter of meticulously examining all the bones individually and comparing them to those of rhinos around the country. The researchers suspected all along that this was a new species, and with the publication of this paper, it is official.
“I’ve been working on these rhinos for almost eight years,” says Short. “To have it done now is very satisfying and I’m excited to contribute to our understanding of North American rhinos.”