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In the Light of Evolution Volume IV: The Human Condition
3.5–3.3-Ma relatively complete but distorted cranium, was found in 1999 at Lomekwi, West Turkana, Kenya. The main reasons Leakey et al. (2001) did not assign this material to Au. afarensis are its reduced subnasal prognathism, anteriorly situated zygomatic root, flat and vertically orientated malar region, relatively small but thick-enameled molars, and the unusually small M1 compared with the size of the P4 and M3. Despite this unique combination of facial and dental morphology, White (2003) claims the new taxon is not justified because the cranium could be a distorted Au. afarensis cranium, but this explanation is not consistent with the small size of the postcanine teeth.
Megadont Archaic Hominins
This grade includes hominin taxa conventionally included in the genus Paranthropus and one Australopithecus species, Australopithecus garhi. The genus Paranthropus, into which Zinjanthropus and Paraustralopithecus are subsumed, was reintroduced when cladistic analyses suggested that the first three species discussed in this section most likely formed a clade. The term megadontia refers to both the absolute size of the postcanine teeth, as well as their relative size when compared with the length of the anterior tooth row.
The taxon Paranthropus robustus Broom 1938 was established to accommodate TM 1517, an associated skeleton recovered in 1938 from the southern African site of Kromdraai B. Other sites that contribute to the P. robustus hypodigm are Swartkrans, Gondolin, Drimolen, and Cooper’s caves, all situated in the Blauuwbank Valley near Johannesburg, South Africa. The dentition is well represented in the hypodigm of P. robustus, but although some of the cranial remains are well preserved, most are crushed or distorted and the postcranial skeleton is not well represented. Research at Drimolen was only initiated in 1992 yet already more than 80 hominin specimens (many of them otherwise rare juvenile specimens) have been recovered and it promises to be a rich source of evidence about P. robustus. The temporal range of the taxon is ca. 2.0–1.5 Ma. The brain, face, and chewing teeth of P. robustus are on average larger than those of Au. africanus, yet the incisor teeth are smaller. The morphology of the pelvis and the hip joint is much like that of Au. africanus; Paranthropus robustus was most likely capable of bipedal walking, but it was probably not an obligate biped. It has been suggested that the thumb of P. robustus would have been capable of the type of grip necessary for the manufacture of simple stone tools, but this claim has not been accepted by all researchers. A second southern African taxon, Paranthropus crassidens, was proposed for the part of the