An early Eocene mammalian fauna from Hengdong, Hunan province, China.

摘要

Rare fossil mammals from Hengdong in the Hengyang Basin of southern China have provided unusual opportunities to study early mammals in depth, to explore their phylogenetic relationships, and shed new light on the early radiation of eutherians. The first mammalian fossil from this basin was recovered fifty years ago. The fauna now includes ten species belonging to seven orders and is characterized by an abundance of early insectivores and rodents and their relatives. It also includes a varied group of mesonychids, didymoconids, and perissodactyls. The species Orientolophus hengdongensis and the new insectivores and rodents are closely related to those from the Bumban Member of the Naran Bulak Formation of Mongolia. New material of Propachynolophus hengyangensis, a species previously considered to be an equoid, suggests that it probably represents either an early tapiroid or a chalicothere, and that equids most likely did not occur in the early Eocene in Asia.; Comparisons of the Hengdong fauna with others provide important information for biostratigraphic correlation and for understanding the mammalian exchange at the very beginning of the Eocene. Nine biozones are recognized from four Asian Paleocene and Early Eocene land mammal ages. The first appearances of the Order Rodentia in the Asian latest Paleocene land mammal age and in the North American Clarkforkian indicate that these land mammal ages may probably be correlated. The Order Perissodactyla marks the beginning of the Eocene. Its first appearance in the Asian early Eocene land mammal age, in the North American Wasatchian, and in the European Sparnacian suggest that these land mammal ages are correlative.; Study and reexamination of the Hengdong fossil mammals indicate that they represent one of the earliest early Eocene faunas in Asia. The Hengdong fauna is correlated with the Mongolian Bumban fauna, the North American Sandcouleean of the Wasatchian, and the European early Sparnacian.