Earliest Miocene hominoid from Southeast Asia

A new hominoid fossil site, Chiang Muan in northern Thailand, yielded the first finding of a large‐bodied Miocene hominoid in Southeast Asia. This specimen (CMu6‐1′00) was preliminarily reported by Kunimatsu et al. ([2000a] Primate Res. 16:299). Later, Chaimanee et al. ([ 2003] Nature 422:61–65) reported additional hominoid teeth from the same site, but all of them were collected from younger deposits (the Upper Lignite Member, in Nagaoka and Suganuma [ 2002] Primate Res 18:159–164). The specimen described here (CMu6‐1′00) was recovered from the Lower Lignite Member (Nagaoka and Suganuma [ 2002] Primate Res 18: 159–164), which is probably several hundred thousand years older than the Upper Lignite Member (Suganuma et al. [ 2002] Primate Res. 18: 165–173). This article provides a detailed description of this hominoid specimen and paleontological/geological data of the fossil site at Chiang Muan. The hominoid specimen (CMu6‐1′00) is an isolated upper molar (right M1 or M2), similar in size to modern orangutans ( Pongo pygmaeus ). This upper molar has low and voluminous cusps, relatively thick enamel, and relatively low relief of the dentine/enamel junction, with only a faint remnant of the lingual cingulum. The age of Chiang Muan is estimated to be the latest Middle Miocene (ca. 11–12 Ma), based on the mammalian fossils (Nakaya et al. [ 2002] Primate Res. 18: 131–141) and paleomagnetic study (Suganuma et al. [ 2002] Primate Res. 18: 165–173). This suggests that the Chiang Muan Hominoid in the present study is an earlier member of Eastern Eurasian Miocene hominoids. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.