ポンダウンの霊長類化石とその年代

ミャンマーの後期始新世のホニュウ類化石相について

抄録

Amphipithecus and Pondaungia are enigmatic fossil primates discovered from the Pondaung district, Central Myanmar (Burma). Since the first discoveries early in this century, many researchers have discussed about their phylogenetic position: some authors regarded them as anthropoid primates (e. g. Pilgrim, 1927; Colbert, 1937), some as a kind of condylarths (Koenigswald, 1965), and others as lemuroid primates (Szalay, 1970; Szalay and Delson, 1979). Even after the second specimens discovered in 1970's, same controversy has been repeated by many researchers (Ba Maw et al., 1979; Ciochon et al., 1985; Ciochon and Holroyd, 1994).
In 1997 several new specimens of Amphipithecus and Pondaungia were discovered in the Pondaung district by Myanmar researchers (Anonymous, 1997). These new fossils provide us a plenty of information about their mandibular morphology, and suggest a possible plylogenetic relationship among Pondaung primates and Siamopithecus, which was discovered from Krabi, Thailand (Chaimanee et al., 1997).
The geological age of the Pondaung primates and Krabi primate have also been discussed by several workers (e. g. Holroyd and Ciochon, 1994; Ducrocq et al., 1992; 1995). In this paper we compared the fossil mammal lists of the Pondaung, Krabi, and several Southern Chinese Eocene faunas. Our conclusion is as follows: the Pondaung fauna is most similar to the Naduo fauna in Yunnan Province, China, and probably slightly older than the Krabi fauna in Thailand. The geological age of the Pondaung fauna is likely to be the Late Eocene rather than the late Middle Eocene advocated by Holroyd and Ciochon (1994).
More detailed comparisons among Middle to Late Eocene mammal faunas in Myanmar, Thailand, China, and Mongolia will make clear the evolutionary history of the Eocene primates in East Asia.