Dictionary of Human Evolution and Biology

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Sahelanthropus Tchadensis Brunét Et Al. 2002

Fossil species composed of six specimens (a cranium, mandibular fragment, and four teeth); recovered from Toros-Menalla locality TM 266, Djurab Desert, northern Chad, in 2001. It has a combination of primitive and derived traits and, consequently, is proposed as a possible stem for the hominid lineage. The holotype is TM 266-01-060-1, a nearly complete, presumed male cranium that was recovered in a dorsoventrally flattened condition. Hominid traits include small canines, no evidence of a sectorial pre-molar or a diastema, and cheek teeth with an enamel thickness that is intermediate between those of later hominids and chimpanzees. Hominoid features are an elongated and small brain case (estimated volume 320-380 cm3) and apelike features of the basicranial skeleton and petrous portion of the temporal bone. Other traits include a massive single supra-orbital torus, small sagittal crest, large ovoid foramen magnum bordered by small occipital condyles, and a large pneumatized mastoid process. There is insufficient data to ascertain whether this species was a habitual biped. The small canine and large brow ridge (suggesting this is a male) implies there was very little sexual dimorphism in canine size. This fossil species suggests that the time period when the chimp-human divergence occurred should be reevaluated.

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