The Ice Age Giants
Artist’s reconstruction of Tibetan woolly rhino that “snow swept” for vegetation. Credit: Julie Naylor
The discovery of a primitive woolly rhino fossil in Tibet suggests that some giant mammals first evolved there before the beginning of the Ice Age.
The finding is published in the journal Science, and is funded by the National Science Foundation (NSF).
The extinction of Ice Age giants such as woolly mammoths, woolly rhinos, giant sloths and saber-toothed cats has been widely studied, but much less is known about where these giants came from, and how they acquired their adaptations for life in a cold environment.
A team of geologists and paleontologists led by Xiaoming Wang from the Natural History Museum of Los Angeles County (NHM) and Qiang Li of Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, uncovered a complete skull and lower jaw of a new species of woolly rhino (Coelodonta thibetana).
The find happened in the foothills of the Himalayas in the southwestern Tibetan Plateau.
"Cold places, such as Tibet and the Arctic and Antarctic, are where the most unexpected discoveries will be made in the future–these are the remaining frontiers that are still largely unexplored," said Wang.
The new rhino is 3.6 million years old (middle Pliocene), much older and more primitive than its Ice Age (Pleistocene) descendants in the mammoth steppes across much of Europe and Asia.
The extinct animal had special adaptations for sweeping snow, using its flattened horn to reveal vegetation, a useful behavior for survival in the harsh Tibetan climate.
Skull and lower jaw of the extinct Tibetan woolly rhino. Credit: Deng Tao
The rhinos lived at a time when global climate was much warmer and the northern continents were free of the massive ice sheets seen in the later Ice Age.
The rhino grew accustomed to cold conditions in high elevations, and became "pre-adapted" for the future Ice Age climate.
When the Ice Age eventually arrived, the cold-loving rhinos simply descended from the high mountains and began to expand throughout northern Asia and Europe.
"This discovery clarifies the origin of the woolly rhinoceros and perhaps much of the now extinct, cold-adapted, large animals that lived in the region of the Himalayas and throughout Eurasia some 2.6 million years ago," said geologist and paleontologist H. Richard Lane of NSF’s Division of Earth Sciences.
Rock exposures in the Himalayas’ Zanda Basin are a paleontologic nirvana for fossil-hunters. Credit: Xiaoming Wang
In addition to the new woolly rhino, the paleontologists uncovered extinct species of three-toed horse (Hipparion), Tibetan bharal (Pseudois, also known as blue sheep), chiru (Pantholops, also known as Tibetan antelope), snow leopard (Uncia), badger (Meles), as well as 23 other kinds of mammals.
The fossil assemblage from Tibet offers new insights into the origin of the cold-adapted Pleistocene megafauna, which has usually been sought in arctic tundra or in cold steppes elsewhere.
The new evidence sets up an alternative scenario: the harsh winters of the rising Tibetan Plateau may have provided the initial step toward cold-adaptation for several successful members of the late Pleistocene mammoth fauna in Europe, Asia, and to a lesser extent, North America.
The Tibetan Plateau may have been another cradle of the Ice Age giants.