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pelvis and the relatively short lower limb suggests that although Au. afarensis was capable of bipedal walking it was not adapted for long-range bipedalism. This indirect evidence for the locomotion of Au. afarensis is complemented by the discovery at Laetoli of several trails of fossil footprints. These provide very graphic direct evidence that at least one contemporary hominin, presumably Au. afarensis, but possibly Kenyanthropus platyops (see below), was capable of bipedal locomotion, but the Laetoli prints are less modern human-like than the 1.5-Ma footprints from Koobi Fora presumed to be of pre-modern Homo (Bennett, 2009). The upper limb, especially the hand (Tocheri et al., 2007) and the shoulder girdle, of Au. afarensis retains morphology that most likely reflects a significant element of arboreal locomotion. Although a recent study argues that sexual dimorphism in this taxon is relatively poorly developed, most researchers interpret it as showing substantial sexual dimorphism [e.g., Kimbel and Delezene (2009)].

The taxon Australopithecus anamensis Leakey, Feibel, McDougall, and Walker 1995 is also presently restricted to East Africa. The type specimen, KNM-KP 29281, was recovered in 1994 from Kanapoi, Kenya. Other sites contributing to the hypodigm are Allia Bay, also in Kenya, and the Middle Awash study area, Ethiopia. The temporal range of Au. anamensis is ca. 4.2–3.9 Ma. The fossil evidence consists of jaws, teeth, and postcranial elements from the upper and lower limbs. Most of the differences between Au. anamensis and Au. afarensis relate to details of the dentition. In some respects the teeth of Au. anamensis are more primitive than those of Au. afarensis (e.g., the asymmetry of the premolar crowns and the relatively simple crowns of the deciduous first mandibular molars), but in others (e.g., the low cross-sectional profiles and bulging sides of the molar crowns) they show some similarities to Paranthropus (see below). The upper limb remains are similar to those of Au. afarensis, and a tibia attributed to Au. anamensis has features associated with bipedality. Researchers familiar with the fossil evidence have suggested that Au. anamensis and Au. afarensis are most likely time successive taxa within a single lineage (Kimbel et al., 2006), with the Laetoli hypodigm of the former taxon intermediate between Au. anamensis and the Hadar hypodigm of Au. afarensis. The taxon Australopithecus bahrelghazali Brunet et al. 1996 is most likely a regional variant of Au. afarensis (Kimbel and Delezene, 2009). But the Chad discovery substantially extended the geographic range of early hominins and reminds us that important events in human evolution (e.g., speciation, extinction) may have been taking place well away from the very small (relative to the size of the African continent) regions sampled by the existing early hominin sites.

The most recently recognized taxon in this grade is Kenyanthropus platyops Leakey et al. 2001. The type specimen, KNM-WT 40000, a ca.

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