東部ユーラシア新第三紀の化石類人猿

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The present fossil evidence indicates that hominoids originated in Africa with the oldest fossil hominoid being probably Kamoyapithecus hamiltoni from the Late Oligocene (25Ma) of Lothidok, northern Kenya. Plenty of hominoid fossils like Proconsul have been found from the early half of the Miocene in East Africa for decades. In the late Early Miocene, some relatively primitive type of hominoids left Africa, and entered into Europe through Anatolia with the oldest hominoid record in Europe being 16.5Ma. In contrast, hominoid fossils of similar ages have not been reported from Eastern Eurasia. It is during the late Middle Miocene (12-13Ma) that hominoids with partly modern aspects appeared both in Western (Dryopithecus) and Eastern (Sivapithecus) Eurasia.In Eastern Eurasia, Neogene hominoid fossils have been discovered mainly in Indo-Pakistan Siwaliks and in the Yunnan Province of southwestern China. Few exceptions were Tinau Khola (South Central Nepal) and Wudu (Gansu Province, China). Recently, a cooperative paleontological research between Thailand and Japan discovered a new Miocene hominoid locality in northern Thailand.Most hominoid fossils collected from Indo-Pakistan Siwaliks are attributed to Sivapithecus with a very few exceptions (“Gigantopithecus and Dryopithecus” or “Hylopithecus” simonsi). The taxonomy of Sivapithecus at the species level is problematic, though three species (S. indicus, S. sivalensis (or punjabicus), and S. parvada) are generally recognised mainly based on their size. Sivapithecus is ranging temporally between the late Middle Miocene (12-13Ma) and the mid-Late Miocene (7-8Ma). Although Sivapithecus is verly likely to be ancestral to living orangutans, their evolutionary history is little known after the disappearance of Sivapithecus from Siwaliks, following the drastic changes in the local paleoenvironments related to the global paleoclimatic changes around 7-8Ma.In East Asia, the best known Neogene hominoid is Lufengpithecus lufengensis from Lufeng (ca. 8Ma) in the Yunnan Province. There are hundreds of craniodental specimens including a few male and female skulls, but the postcranial material is very rare. Lufengpithecus lufengensis was once thought to be two different taxa: Sivapithecus yunnanensis for larger specimens and Ramapithecus lufengensis for smaller specimens. However, as Ramapithecus in Siwaliks was synnoymized to Sivapithecus, the Lufeng material also came to be considered to represent a single species with a very high degree of sexual dimorphism. Because the Lufeng material lacks some of the possible shared derived cranial characters between Sivapithecus and orangutans, a new genus Lufengpithecus was created by Wu (1987).In addition to the above mentioned fossil hominoids, the subjects of this article include other less known fossil hominoids and the paleoenvironments of the Neogene Eastern Eurasia.
2002-10-01

東部ユーラシア新第三紀の化石類人猿

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