Sunday 19 January 2014

Rhinoceros teeth from the Early Miocene of Gansu Province, China.

Rhinoceroses are iconic members of the modern Mammalian megafauna, distinguished by their large bulk, thick hides and horns. There are five modern species of Rhinoceros from Africa and Asia, three of which are considered to be Critically Endangered under the terms of the International Union for the Conservation of Nature's Red List of Endangered Species, with the two remaining being considered Vulnerable and Near Threatened. The earliest Rhinoceroses appear in the fossil record in the Early Eocene in North America. These animals were more Horse-like than Rhinoceros-like in appearance, and the smallest were no bigger than a Dog. 

In a paper published in the journal Vertebrata PalAsiatica in April 2013, Deng Tao of the Key Laboratory of Vertebrate Evolution and Human Origin and Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences reports the discovery of a number of tusk-like lower incisors attributed to the early Rhinoceros Aprotodon lanzhouensis from the Early Miocene Shangzhuang Formation of the Linxia Basin in Gansu Province in northwest China.

Tusk like lower incisors of Aprotodon lanzhouensis from the Early Miocene Shangzhuang Formation of the Linxia Basin in Gansu Province in northwest China. Deng (2013).

Rhinos of the genus Aprotodon are known from the Late Eocene to Early Miocene of Central, South and East Asia. There are four described species, all known only from their skulls and teeth. The genus is noted for its large tusks, which have been compared to those of Hippos, and it has been suggested that these Rhinos had a similar lifestyle.

Aprotodon lanzhouensis has previously been reported from the Late Eocene of Mongolia, and from the Linxia and Lanzhou Basins of northwest China as well as sites in Pakistan and Kazakhstan in the Oligocene and early Miocene, disappearing by the Middle Miocene. Deng notes that this was a time of falling temperatures and increasing aridity across much of Asia, and that despite its Hippo-like dentition Aprotodon lanzhouensis appears to have been restricted to drier areas; it is notably absent from the several sites in eastern Yunnan, which have produced abundant Mammal specimens (including other types of Rhino) from the same period but a warmer, wetter climate. He suggests that if Aprotodon lanzhouensis did have an aquatic, Hippo-like lifestyle, then it was restricted to rivers in areas of dry, open woodland.

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