SHORT COMMUNICATION Yutaka Kunimatsu Æ Benjavun Ratanasthien Hideo Nakaya Æ Haruo Saegusa Æ Shinji Nagaoka Yuˆsuke Suganuma Æ Akira Fukuchi Æ Bantita Udomkan An additional specimen of a large-bodied Miocene hominoid from Chiang Muan, northern Thailand Received: 12 July 2003 / Accepted: 29 April 2004 / Published online: 12 August 2004 Ó Japan Monkey Centre and Springer-Verlag 2004 Abstract Chiang Muan is the first Miocene fossil site in Southeast Asia, from which large-bodied Miocene hominoids have been discovered (Kunimatsu et al., Primate Res 16:299, 2000a). In this article, we describe a hominoid lower molar (CMu15-5¢01) recovered from the Upper Lignite Member of Chiang Muan. The age of Chiang Muan is estimated to be latest Middle or earliest Late Miocene (around 11 Ma), based on the mammalian fauna. Keywords Thailand Æ Miocene Æ Hominoidea Æ Southeast Asia Æ Lufengpithecus Introduction In eastern Eurasia, Sivapithecus is well known from the Siwaliks in India and Pakistan between 7.5 and 12.5 Ma (Kappelman et al. 1991). Hundreds of Lufengpithecus specimens have been recovered from Lufeng and Yu- anmou in Yunnan Province of the People’s Republic of China. Both sites are dated to the mid-Late Miocene, around 8–9 Ma (Ni and Qiu 2002). A few hominoid fossils have been found from the Xiaolongtan lignite mine in Kaiyuan County, Yunnan Province, since the 1950s (Woo 1957, 1958; Zhang 1987). They are also assigned to Lufengpithecus by recent authors (Harrison et al. 2002; Zheng and Zhang 1997), but are older in geological age (ca. 10–11 Ma: Dong 1987; Qiu and Qiu 1995). All of the above-mentioned Neogene hominoid sites in eastern Eurasia are located north of the Tropic of Cancer. In more southern areas, such as the Indochina peninsula and Southeast Asian archipelago, the evolu- tionary history of hominoids is poorly known. No Neogene hominoid fossils have been discovered from Southeast Asian countries until recently. Kunimatsu et al. (2000a) reported a large-bodied Miocene hominoid fossil (CMu6-1¢00, an isolated upper molar) from a lig- nite mine of Chiang Muan, northern Thailand. Nearly 2 years after this first finding, a second hominoid fossil (CMu15-5¢01) was also discovered at this site. In addi- tion, a French–Thai group separately reported more hominoid fossils from the same lignite mine (Chaimanee et al. 2003). They provisionally assigned their material to a new species of Lufengpithecus (cf. L. chiangmuanensis). Methods Study area The fossil-yielding site is a lignite mine in the Chiang Muan basin in northern Thailand. By the end of the field season in December 2002, 18 fossil localities Y. Kunimatsu (&) Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484-8506, Japan E-mail: kunimats@pri.kyoto-u.ac.jp B. Ratanasthien Æ B. Udomkan Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand H. Nakaya Faculty of Engineering, Kagawa University, Kagawa, Japan H. Saegusa Himeji Institute of Technology, Hyogo, Japan S. Nagaoka Faculty of Education, Nagasaki University, Nagasaki, Japan Y. Suganuma Ocean Research Institute, University of Tokyo, Tokyo, Japan A. Fukuchi Faculty of Science, Okayama University, Okayama, Japan Primates (2005) 46:65–69 DOI 10.1007/s10329-004-0096-6