Analysis of the dental morphology of Plio-Pleistocene hominids. V. Maxillary postcanine tooth morphology.

A total of 139 maxillary molar crowns and 79 maxillary premolar crowns, from at least 98 individual East and Southern African Plio-Pleistocene hominids, has been subjected to detailed morphometric analysis. All but 16 of the 98 specimens were assigned to taxonomic categories identified as EAFROB, EAFHOM, SAFGRA, SAFROB and EAFHER. The analysis was based on whole crowns and the component cusps. While there was variable overlap between the ranges of measured crown base area of the two Southern African taxa, there was little, or no, overlap between the two major East African taxonomic categories. Crown shape distinguished EAFHOM from the three other australopithecine taxa, especially for P3, P4 and M1. Of the non-metrical traits, the expression of Carabelli's complex and the incidence of a distal cuspule discriminate best between the categories. Analysis of the absolute and relative cusp area data shows that the major taxonomic distinction in relative cusp area is in the premolars, in which it is apparent that EAFROB are distinguished by their larger buccal cusps. The principal conclusions of the assessment of the specimens in the 'unknown' category is that the postcanine dentitions of a skull, KNM-ER 1805, and a cranium, KNM-ER 1813, are closest in size and shape to EAFHOM. There is no dental evidence to suggest that these specimens should be assigned to A. africanus, the formal taxon making up the SAFGRA category.