Bovidae (Mammalia, Artiodactyla) from the Neogene Irrawaddy beds, Myanmar

摘要

The evolution of the Neogene bovids (Mammalia, Artiodactyla, Ruminantia) in central Myanmar was examined, with descriptions of new specimens of caprine and bovine bovids from the upper Miocene to Pliocene part of the Irrawaddy beds. In the early lace Miocene of central Myanmar, bovids had a relatively low diversity and were represented by Helicoportax sp. and Selenoportax vexillarius. Thereafter, they rapidly diversified until the latest Miocene (c. 6 Ma), including a caprine species (Caprinae gen. et sp. indet.) with spiral horn cores and seven bovines - Sivaportax dolabella, tragoportax sp., Selenoportax vexillarius, Selenoportax falconeri, Pachyportax latidens, Pachyportax giganteus, and Proleptobos birmanicus. The latest Miocene/early Pliocene bovids are characterised by the coexistence of the Irrawaddy-endemic species (Sivaportax dolabella and Proleptobos birmanicus) and the other genera/species shared with the Nagri/Dhok Pathan faunas of the Siwaliks of Indo-Pakistan (Tragoportax, Selenoportax vexillarius, Selenoportax falconeri, Pachyportax latidens, and Pachyportax giganteus). Among them, only the endemic species had survived throughout the Pliocene. The occurrence of Duboisia (Pleistocene bovids in Java, Indonesia) from the upper parr (upper Pliocene) of the Irrawaddy beds also supports the dominance of endemic species in Southeast Asia. Through the late Neogene, no typical faunal turnovers were demonstrated in the Irrawaddy bovids with respect co chose in the Siwalik bovids. This relatively low turnover rate was possibly affected by the progress in the faunal isolation of central Myanmar from the fauna of Indo-Pakistan during the late Pliocene owing to the formation of biogeographical barriers between central Myanmar and South Asia.