Rare fossils reveal new ‘bone-crushing’ dog

A newly identified species of ancient animal was a coyote-sized dog and a member of an extinct subfamily commonly known as bone-crushing dogs because of their powerful jaws and broad teeth, says Steven Jasinksi. "In this respect they are believed to have behaved in a similar way to hyenas today." (Credit: Eli Duke/Flickr)

Fossils have revealed a new species of dog that would have roamed the coast of eastern North America approximately 12 million years ago, when massive sharks like megalodon swam in the oceans.

The newly named species, Cynarctus wangi, was a coyote-sized dog and 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,” says lead author Steven E. Jasinski, a student in the Earth and environmental science department at the University of Pennsylvania and acting curator of paleontology and geology at the State Museum of Pennsylvania.

Cynarctus / Cynarctus wangi
Illustration of Cynarctus. (Credit: Mauricio Antón from Dogs, Their Fossil Relatives and Evolutionary History.)

Because fossils from terrestrial species from this region and time period are relatively rare, the find helps fill in important missing pieces about what prehistoric life was like on North America’s East Coast, researchers say.

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“Most fossils known from this time period represent marine animals, who become fossilized more easily than animals on land,” Jasinski says. “It is quite rare we find fossils from land animals in this region during this time, but each one provides important information for what life was like then.”

As reported in the Journal of Paleontology, when researchers first began their investigation of the specimen, which had been found by an amateur collector along the beach under the Choptank Formation in Maryland’s Calvert Cliffs region and was then held by the Smithsonian Institution, they presumed it was a known species of borophagine dog, a species called marylandica that was questionably referred to as Cynarctus, a fossil of which had been found in older sediment in the same area.

But when they compared features of the occlusal surfaces, where the top and bottom teeth meet, of the previously known and the new specimens, they found notable differences. They concluded that the specimen represented a distinct species new to science. “It looks like it might be a distant relative descended from the previously known borophagine,” Jasinski says.

Borophagine dogs were widespread and diverse in North America from around 30 million to about 10 million years ago. The last members went extinct around 2 million years ago during the late Pliocene. C. 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.

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Despite its strong jaws, the researchers believe C. 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 says. “It would have supplemented that by eating plants or insects, living more like a mini-bear than like a dog.”

Although C. 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 says.

Other researchers from the University of Pennsylvania and from East Tennessee State University are coauthors of the study that was funded in part by the National Science Foundation.

Source: University of Pennsylvania