A team of paleontologists has discovered a new species of fossil dog that was about the size of a coyote and lived on the coast of eastern North America in the middle Miocene, approximately 12 million years ago.

Fossilized remains of the ancient dog, which was named Cynarctus wangi, were recovered from the Choptank Formation (Chesapeake Group) of Maryland.

According to the authors, Steven Jasinski from the University of Pennsylvania and Prof. Steven Wallace from East Tennessee State University, Cynarctus wangi was a member of the extinct subfamily Borophaginae, commonly known as bone-crushing dogs because of their powerful jaws and broad teeth.

“In this respect they are believed to have behaved in a similar way to hyenas today,” Jasinski said.

Borophagine dogs were widespread and diverse in North America from 30 to 10 million years ago. The last members went extinct around 2 millions years ago.

Cynarctus wangi represents one of the last surviving borophagines and was likely outcompeted by ancestors of some of the canines living today: wolves, coyotes and foxes.

Despite its strong jaws, the team believes Cynarctus wangi wouldn’t have been wholly reliant on meat to sustain itself.

“Based on its teeth, probably only about a third of its diet would have been meat,” Jasinski explained.

“It would have supplemented that by eating plants or insects, living more like a mini-bear than like a dog.”

Although Cynarctus wangi represents the first known carnivore from the Choptank Formation, some of the animals that it would have lived beside are known.

These include the ancient pigs Desmathyus and Prosthenops, the horned artiodactyl Prosynthetoceras, an ancient elephant-like animal known as a gomphothere, and perhaps the ancient horse Merychippus.

“This new dog gives us useful insight into the ecosystem of eastern North America between 12 and 13 million years ago,” Jasinski said.

The research was detailed online in the Journal of Paleontology.

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Steven E. Jasinski & Steven C. Wallace. 2016. A Borophagine canid (Carnivora: Canidae: Borophaginae) from the middle Miocene Chesapeake Group of eastern North America. Journal of Paleontology, vol. 89, no. 6, pp. 1082-1088; doi: 10.1017/jpa.2016.17