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Sahelanthropus
''Sahelanthropus tchadensis'' is an extinct hominine species that is dated to about , possibly very close to the time of the chimpanzee–human divergence. It is unclear whether it can be regarded as a member of the Hominini tribe.〔 Few specimens are known, other than the partial skull nicknamed ''Toumaï'' ("hope of life").
==Fossils ==
Existing fossils include a relatively small cranium named Toumaï ("hope of life" in the local Daza language of Chad in central Africa), five pieces of jaw, and some teeth, making up a head that has a mixture of derived and primitive features. The braincase, being only 320 cm³ to 380 cm³ in volume, is similar to that of extant chimpanzees and is notably less than the approximate human volume of 1350 cm³.
The teeth, brow ridges, and facial structure differ markedly from those found in ''Homo sapiens''. Cranial features show a flatter face, u-shaped dental arcade, small canines, an anterior foramen magnum, and heavy brow ridges. No postcranial remains have been recovered. The only known skull suffered a large amount of distortion during the time of fossilisation and discovery, as the cranium is dorsoventrally flattened, and the right side is depressed.〔
Because no postcranial remains (i.e., bones below the skull) have been discovered, it is not known definitively whether ''Sahelanthropus tchadensis'' was indeed bipedal, although claims for an anteriorly placed foramen magnum suggests that this may have been the case. Upon examination of the foramen magnum in the primary study, the lead author speculated that the utilisation of a bipedal gait "would not be unreasonable" based on basicranial morphology similar to more recent hominids. Some palaeontologists have disputed this interpretation, stating that the basicranium, as well as dentition and facial features, do not represent adaptations either unique to the hominid clade or indicative of bipedalism. Its canine wear is similar to other Miocene apes. Moreover, according to recent information, the femur of a hominid might have been discovered alongside the cranium but never published.〔Hawks 2009 ("''Sahelanthropus'': The femur of Toumaï?" )〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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