Rodent faunas, their paleogeographic pattern, and responses to climate changes from the early Eocene to the early Oligocene in Asia

Abstract

Rodents are an important component in Paleogene terrestrial ecosystems. Their evolution and faunal turnover have likely been influenced and triggered by global climate change. Here, we compiled rodent faunas from the early Eocene to the early Oligocene in Asia to discuss rodent faunal turnover and its correlation with paleogeographic and paleoclimate changes. Successive rodent faunas from the early Eocene to the early Oligocene are recorded in East Asia, and rodent faunal turnover is obviously affected by paleoclimatic changes. During the Ulangochuian (after the middle Eocene climatic optimum), when temperatures declined slowly, the East Asian rodent fauna showed a clear decline in generic diversity and a transformation from ctenodactyloid-dominant to cricetid–dipodid-dominant faunas. During the Eocene–Oligocene transition (EOT) and global cooling, the East Asian rodent fauna exhibited a considerably high generic diversity of cricetids, dipodids, and ctenodactylids. The low temperatures during the Ulangochuian and Ergilian in East Asia served as a habituation ground for the cricetids and dipodids, which became preadapted for the EOT, successfully helping rodents become dominant faunas after EOT. The rodent faunas in South Asia formed a relatively unique group in much of the Eocene and early Oligocene; sometimes, they were closer to European or African than to Asian rodents. The greatly different paleoenvironment probably caused striking differences between the rodent faunas in South Asia and East Asia.