Miocene Mammalian Faunas of Northern Thailand and Their Geological Age

The joint Japan-Thailand expedition surveyed the Miocene basins in Northern Thailand from 1996 to 2002. The Miocene sediments in the Northern Thailand yield many vertebrate fossils. Mammalian faunas from the Northern Thailand resemble those from the Middle Miocene of the Siwaliks in Pakistan according to previous works. We examined the vertebrate fauna of the three Miocene sites, Mae Soi, Chiang Muan, and Sop Mae Tham of the Northern Thailand.At Mae Soi 50km south west of Chiang Mai, a primitive amebelodontid gomphothere, Archaeobelodon, and equids was collected, At Chiang Muan Lignite Mine 150km east of Chiang Mai (the Chiang Muan Formation), we found fossils of a large ape, suines, and a primitive tetralophodont gomphothere. The mammalian fauna from the Chiang Muan Formation suggests the latest Middle Miocene age. At Sop Mae Tham, we found a new Late Miocene fauna. It includes the Hipparionini (Equidae), which has never been recorded in the Neogene of Southeast Asia. The Sop Mae Tham mammal fauna consists of tetralophodont gomphotheres, rhinocerotid, hipparionin equids, Listriodon and suine, tragulids, Boselaphini and primitive bovids. This mammalian assemblage suggests the early Late Miocene age.