Fossil jawbones and teeth of a highly predatory fox have been found in the Himalayas. Researchers say this new extinct fox is likely the ancestor of modern arctic foxes (Vulpes lagopus), suggesting that Tibet may have been a cradle of evolution for cold-adapted animals of the Ice Age and today.
Known as the “third pole” of the world, the Himalayan-Tibetan Plateau is a vast frozen terrain -- it’s like the Arctic and the Antarctic, but at a low latitude. Despite thousands of kilometers between them, mammals now living in the arctic and in high-altitude Tibet share similar adaptions: the long, thick winter fur of arctic muskox and Tibetan yak, as well as a more predatory niche for carnivores.
The newly discovered Tibetan fox, Vulpes qiuzhudingi, was discovered in rocks that are between 3.60 million and 5.08 million years ago. And while it bears a striking resemblance to modern arctic foxes, the Pliocene fox substantially predates the oldest records for arctic foxes. “They are the first Arctic-fox-like fossils to be found from outside the Arctic regions, and they pre-date the oldest records by 3 million to 4 million years,” study author Xiaoming Wang from the Natural History Museum of Los Angeles County tells Nature. “The scenario seems to be clear that we have an ancestor of Arctic foxes in high Tibet.”
An excavation crew discovered the nearly complete left lower jawbone in the “layer cake” sediments of the Zanda Basin in the Himalaya Range during August 2010. Wang’s team would camp at sites as high as 4,730 meters above sea level (where water freezes every night), and team members would disband every morning to walk alone in search of fossils. Various other fragments have also been uncovered at the Kunlun Pass Basin in Tibet’s Kunlun Mountain.
In this picture of the “highly hypercarnivorous” dentition, you can see how the first lower molar (the big one) has a cutting edge, good for slicing meat. “The new Tibetan species and the Arctic fox show striking similarity in their dental adaptation for extreme meat-eating,” Wang explains. Most other species of modern foxes are omnivores.
Like polar bears and gray wolves adapted to harsher climates, the Tibetan fox’s highly predatory lifestyle was likely a consequence of the scarce food resources during winter months and their high energetic requirements in freezing temperatures.
This apparent connection between an ancestral high-elevation species and its modern polar descendant lends support to the “Out-of-Tibet” hypothesis -- which suggests that Tibet during the Pliocene was a training ground for cold-environment adaptations way before the start of the Ice Age, around 2.6 million years ago.
Other scenarios suggest an arctic tundra origin for cold-adapted megafauna, including woolly mammoths, saber-toothed cats, and giant sloths. Wang and his team argue that these Ice Age superstars had Tibetan ancestors who were pre-adapted to severe environments; when ice sheets advanced, they come down from the mountains and spread along the cold steppes in Northern Eurasia and North America.
Here’s a map of the Pliocene Tibetan fox localities (stars), Late Pleistocene arctic fox localities (circles), and the distribution of modern arctic foxes. The Tibetan Plateau is separated from the nearest modern arctic fox range by at least 2,000 kilometers.
"The concept 'Out of Tibet' is an exciting insight for the origin of cold-adapted mammals of the Pleistocene," National Science Foundation's Rich Lane says in a news release. "It parallels the 'Out of Africa' theory for the evolution of hominids. Together they may be a model for wider application in biological history and geography."
The newly discovered species is about the size of a large male red fox (Vulpes vulpes) and about 20 percent larger than living and late Pleistocene arctic foxes. The researchers named it in honor of paleontology professor Qiu Zhuding of the Chinese Academy of Sciences.
Twenty or so extinct mammal species were also discovered in the same area, including: woolly rhino (Coelodonta thibetana), three-toed horse, Tibetan bharal (or blue sheep), chiru (Tibetan antelope), snow leopard (Uncia uncial), and hunting dog (Sinicuon dubius).
The work was published in Proceedings of the Royal Society B this week.
Images: Julie Selan (reconstruction) & Xiaoming Wang (map, jawbones)