Kenyanthropus platyops

Click here for the full article by Leakey et al. in Nature outlining Kenyanthropus (could take some time to download)

Phylogeny Discussion

Crania

The main morphological distinctions regarding this specimen are derived from the crania. The overall size of the skull (KNM-WT 40000) falls within the range of Australopithecus afarensis and Australopithecus africanus, and has a moderate postorbital constriction. It has a stepped nasal cavity entrance and a weak midline subnasal prognathism. The teeth have thick enamel and the upper molars are comparatively small. It has a thin palate, as seen in later Homo such as H. rudolfensis. The initial suprarbital orientation of the temporal lines is higher than that of robust Australopithecines. It has an anteriorly positioned zygomatic process of maxilla. It has one half of the foramen magnum preserved, which suggests a more oval shape, as opposed to the heart shaped of early robust Australopithecines (Leakey et al, 2001).

Dental

Only the right M² crown is preserved enough to allow reliable dental comparisons. It is particularly small and falls below the known ranges in size of other early hominin species. An estimation of the size of the M¹ proves to be, at the most, at a minimum of the values for A. anamensis, A. afarensis and H. habilis (Leakey et al, 2001).

Conclusion

It is argued that KNM-WT 40000 lacks almost all of the derived features of Paranthropus (Leakey et al, 2001). On the basis of facial morphology, the specimen also does not show the derived features associated with Homo, excluding H. rudolfensis and H. habilis. This leaves the genus Australopithecus as the last possibility, but again due to its derived face and small molar size that it stands apart from the species named to this genus. Though morphology seems to separate it from other known hominid ancestors, with an accurate dating of 3.5 ma putting it as a contemporary of A. afarensis, it is not certain where in the phylogenetic “bush” this recently discovered species will lie. One possibility, which is merely hypothetical, is found on the first Kenyanthropus page on this web site.