GRAY, Tenn. — Researchers at East Tennessee State University discovered an upper arm bone of an animal that they believe to be a member of an extinct group more commonly called “bone-crushing dogs.”
Overseen by the Don Sundquist Center of Excellence in Paleontology at ETSU, researchers have studied the Gray Fossil Site for over 20 years. During this time, they have identified many extinct animal and plant species. ETSU said that while large herbivores are well known from the site, large predators are relatively uncommon, including only alligators and scarce remains of at least one sabertooth cat.
ETSU officials said a recent study published in the Journal of Paleontology describes a single right humerus of an animal named Borophagus, a member of an extinct group more commonly called bone-crushing dogs. The animal is named for its strong teeth and jaws. This is the first evidence of any animals in the dog family from the Gray Fossil Site.
Researchers compared the single limb bone with those of a wide range of modern and fossil dogs, allowing them to estimate the size of the extinct dog. ETSU said researchers believe the dog would have weighed between 115 to 160 pounds, making the Borophagus similar in size to the largest living wolves worldwide.
Researchers said that the humerus (upper arm bone) is stout and has large areas where muscles once attached. This suggests this ancient carnivore was a mighty ambush hunter rather than a pursuit predator like wolves.
“The identification of a bone-crushing dog adds to the list of terrestrial apex predators at the Gray Fossil Site, the other being a sabertooth cat,” said Emily Bōgner, a doctoral student at the University of California, Berkeley, and alumnus of ETSU’s paleontology master’s program. “With two large predators on land and alligators in the water, herbivores at the site would have had to be on high alert.”
Associate professor in the ETSU Department of Geosciences and curator at the Gray Fossil Site and Museum also assisted in conducting the research.
ETSU said the Gray Fossil Site also represents a new habitat for extinct dogs.
Researchers said these creatures are known from dozens of fossil sites across the United States and Mexico but are usually found alongside plants and animals in open environments like grasslands. However, fossils at Gray paint a picture of densely forested habitats with many forest plants and tree-dwelling animals. Researchers said that the ambush hunting strategy of bone-crushing dogs has been particularly well-suited for hunting large herbivores in the ancient forests of the Appalachian mountains.
“The limb proportions of the Borophagus are a conundrum to researchers,” Bōgner said. “Having more limb bones would be a big help in understanding how these bone-crushing dogs moved.”
“Since the lifestyle of these dogs is thought to be similar to hyenas, I would also like to see bones that had been cracked open by Borophagus at the site,” Samuels said. “That could help us to understand what they were actually eating in the ancient Appalachian forests.”
