September 1, 2011. Copyright 2011, Graphic News. All rights reserved

An evolutionary “cradle” for megaherbivores

LONDON, September 1, Graphic News: The frosty highlands of the Tibetan Plateau may have been an evolutionary “cradle” for the woolly rhinos and other shaggy, cold-hardy creatures that roamed North America and Eurasia during the last Ice Age, a new study suggests.

A paper published in the September 2 issue of the journal Science reveals the discovery of a primitive woolly rhino fossil in the Himalayas. The find suggests some giant mammals were present in present-day Tibet long before the beginning of the Ice Age.

The extinction of Ice Age giants such as woolly mammoths and rhinos, giant sloths, and sabre-tooth cats has been widely studied, but much less is known about where these giants came from, and how they adapted to live in a cold environment.

A team of geologists and paleontologists, led by Xiaoming Wang from the Natural History Museum of Los Angeles County and Qiang Li of the 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) in 2007, in the foothills of the Himalayas in the southwestern Tibetan Plateau.

“Cold places, such as Tibet, 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 Dr. Wang.

Coelodonta thibetana is 3.6 million years old, much older and more primitive than its Ice Age descendants -- C. tologoijensis and C. antiquitatis -- which inhabited the steppes across much of Europe and Asia. The extinct animal had developed special adaptations for sweeping snow using its flattened horn to reveal vegetation, a useful behaviour for survival in the harsh Tibetan climate.

The rhino accustomed itself to cold conditions in high elevations and became pre-adapted for the future Ice Age climate. When the Ice Age eventually arrived around 2.6 million years ago, the new paper posits, the cold-loving rhinos simply descended from the high mountains and began to expand throughout northern Asia and Europe.

In addition to the new woolly rhino, the paleontologists also 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), and 23 other kinds of mammals.

The team’s new fossil assemblage from Tibet offers new insights into the origin of the cold-adapted Pleistocene epoch megafauna, which has usually been sought either in the Arctic tundra or in the cold steppes elsewhere. This new evidence offers an alternative scenario: the harsh winters of the rising Tibetan Plateau may have provided the initial step towards cold-adaptation for several subsequently successful members of the late Pleistocene mammoth fauna in Europe, Asia, and to a lesser extent, North America.
/ENDS