Researchers working in what’s now Maryland have unearthed the fossilized tooth of a new dog species that roamed North America’s east coast some 12 million years ago. Cynarctus wangi was a coyote-sized member of the “bone-crushing” dog lineage, and it's described in the Journal of Paleontology this week.
The fossilized right upper second molar was discovered by an amateur collector along the beach by the middle Miocene Choptank Formation in the Calvert Cliffs of Maryland. It belonged to a canid – the family of carnivores ranging from raccoon dogs and foxes to jackals and wolves – and more specifically, it was a member of an extinct subfamily called Borophaginae. These are commonly known as the “bone-crushing dogs.” At the time, researchers thought it was a previously described species known as Cynarctus marylandica. (Since that species is only known from teeth in the lower jaw, the genus remains questionable.) Cynarctus marylandica is one of only three known borophagine dogs from the northeastern U.S.
Now, Steven Jasinski from the State Museum of Pennsylvania and Steven Wallace of East Tennessee State University have reexamined the specimen. Called USNM 534040, the molar is 13.44 millimeters (1.3 centimeters) at its longest and 11.77 millimeters (1.2 centimeters) at its widest. After comparing the occlusal surfaces (where the top teeth touch down on the bottom teeth) of known and new specimens, they found enough differences to warrant a new species.
Cynarctus wangi is named after Xiaoming Wang of the Natural History Museum of Los Angeles County for his work with fossil canids and carnivores. It appears to represent the next evolutionary stage of Cynarctus marlyandica, which was found in older sediments of the same Chesapeake Group.
Borophagine dogs were widespread and diverse in North America from around 30 million to about 10 million years ago. Like other borophagine dogs, Cynarctus wangi had powerful jaws and broad teeth, and it likely behaved like spotted hyenas today. But it was a hypocarnivore that didn’t rely on just meat. "Based on its teeth, probably only about a third of its diet would have been meat," Jasinski said in a statement. "It would have supplemented that by eating plants or insects, living more like a mini-bear than like a dog."
The last of the borophagine dogs went extinct around 2 million years ago during the late Pliocene – likely outcompeted by ancestors of today's wolves, coyotes, and foxes.