The oldest arctic fox remains have teeth you would not want to face.
Scientists unearthed the fossils of the newly identified, extinct fox, an ancient sharp-toothed predator called Vulpes qiuzhudingi, which lived 4.6 to 5.08 million years ago in the Pliocene period. They could make them the earliest known ancestor of today's arctic fox, according to the study published June 10 in the journal Proceedings of the Royal Society B.
From 2006 to 2012, the three jaw fossils were dug up in Tibet's Zanda Basin and Kunlun Mountains. The find supports the "out of Tibet" theory, which argues that the plateau served as a "third Pole" where cold-blooded predators lived until they migrated to new lands at the beginning of the Ice Age, about 2.6 million years ago. It would be at this time that the arctic fox moved toward the vast expanse of Russia, Siberia and Northern Canada.
In 2010, the team discovered an exemplar fossil of a jaw still studded with teeth. Never has bad breath been so foxy.
"I first uncovered part of the lower molar, and immediately I knew it was some kind of a dog," said study co-author Zhijie Jack Tseng, a paleobiologist at the American Museum of Natural History in New York City.
It's worth pointing out that many dogs belong to the same family as foxes, so these predators could very well have had a case of dog breath. As Tseng and colleagues began examining them, they found the teeth had a "striking resemblance" to those of the arctic fox. The fossils are sharper and the lower molars lack cusps, which are the elevation on the surface of posterior teeth. This adaption allowed prehistoric predators to tear into prey, signaling that the fox was a hypercarnivore.
Hypercarnivores bare bigger, sharper teeth whereas omnivorous foxes have duller molars designed for chewing plants, small vertebrates and insects. Since polar animals require a thicker coat to insulate them from the cold, it makes sense that these extinct foxes fall under the category of hypercarnivores.
So, what sort of animals did these foxes eat? Other fossils found near the foxes' remains in Tibet range from squirrels to pikas to voles, all of which are small mammals that today's arctic fox would eat.
Although other scientists question whether this new species fits the ancient fox theory, Tseng has been eager at work.
"It's exciting to see as [Tseng's group] fleshes out this theory species by species," concluded University of South Carolina carnivore paleontologist Dr. Adam Hartstone-Rose.