By reconstructing the changing diets of elephants in the last two million years in China, an international research team has unearthed clues to the extinction of two prehistoric elephant species. The research was published in Quaternary International.
Although elephants today live only in remote, tropical parts of Africa and South Asia, they were widespread before the Ice Ages. The elephant species Stegodon went extinct around 11,000 years ago at the end of the Pleistocene, coinciding with the worldwide disappearance of large mammal species at the time—including the iconic woolly mammoths, giant deer and saber-toothed cats.
The Asian elephant, on the other hand, survived in Southern China into historical times. PhD student Mr. Zhang Hanwen at the University of Bristol, UK, collaborated with researchers at the Chinese Academy of Sciences on the study. The researchers sampled 27 fossilized elephant teeth for tiny wear patterns called microwear, using a digital microscope to capture the 3D surface textures of the teeth. The textures were analyzed to identify what the elephants were eating in the days and weeks before they died. “We are talking huge, brick-sized molars here—the largest of any animal, but the signs of tooth wear are tiny, down to thousandths of a millimeter,” said Zhang.
By comparing this data with the diets of modern ruminants such as deer, antelopes and oxen, the researchers concluded that two extinct elephants from Southern China, Sinomastodon and Stegodon, primarily browsed on leaves, and not on grass. The third, Elephas, which includes the modern Asian elephant, incorporated both grass and leaves in its diet.
According to their findings, the researchers estimate that Sinomastodon and Stegodon coexisted in Southern China between 2.6 and one million years ago. Sinomastodon then became extinct, leaving Stegodon to become the dominant elephant in Southern China for the remainder of the Pleistocene. “Forests were on the decline, alongside many of the more archaic mammal species that inhabited them. The highly evolved molars of Stegodon, with multiple enamel ridges, might have allowed it to browse on its preferred foliage in a more efficient way, thus outcompeting Sinomastodon, which preferred the same diet, but had less sophisticated molars consisting of large, blunt, conical cusps,” explained Zhang.
The article can be found at: An Examination of Feeding Ecology in Pleistocene Proboscideans from Southern China (Sinomastodon, Stegodon, Elephas), by Means of Dental Microwear Texture Analysis. Read more from Asian Scientist Magazine at: http://www.asianscientist.com/
2016/08/in-the-lab/elephant- teeth-surface-texture-south- china-elephas-stegodon- sinomastodon/–