The skull of StW 573, a 3.67 Ma Australopithecus skeleton from Sterkfontein Caves, South Africa

Here we present the first full anatomical description of the 3.67 million-year-old Australopithecus skull StW 573 that was recovered with its skeleton from the Sterkfontein Member 2 breccia in the Silberberg Grotto. Analysis demonstrates that it is most similar in multiple key morphological characters to a group of fossils from Sterkfontein Member 4 and Makapansgat that are here distinguished morphologically as A. prometheus. This taxon contrasts with another group of fossils from those sites assigned to A. africanus. The anatomical reasons for why these groupings should not be lumped together (as is frequently done for the South African fossils) are discussed in detail. In support of this classification, we also present for the first time a palate (StW 576 from Sterkfontein Member 4) newly reconstructed by RJC, which has a uniquely complete adult dentition of an A. africanus. The StW 573 skull also has certain similarities with other earlier Australopithecus fossils in East Africa, A. afarensis and A. anamensis, which are discussed. One of its most interesting features is a pattern of very heavy anterior dental wear unlike that found in A. africanus but resembling that found in A. anamensis at 4.17 Ma. While StW 573 is the only hominid fossil in Sterkfontein Member 2, we conclude that competitive exclusion probably accounts for the synchronous and sympatric presence of two species of Australopithecus in the younger deposits at Makapansgat and Sterkfontein Member 4. Because the StW 573 skull is associated with a near-complete skeleton that is also described for the first time in this special issue, we are now able to use this individual to improve our understanding of more fragmentary finds in the South African fossil record of Australopithecus.

The diets of ungulates from the hominid fossil-bearing site of Elandsfontein, Western Cape, South Africa

The dietary regimes of 15 ungulate species from the middle Pleistocene levels of the hominid-bearing locality of Elandsfontein, South Africa, are investigated using the mesowear technique. Previous studies, using taxonomic analogy, classified twelve of the studied species as grazers (Redunca arundinum, Hippotragus gigas, Hippotragus leucophaeus, Antidorcas recki, Homoiceras antiquus, Damaliscus aff. lunatus, Connochaetes gnou laticornutus, Rabaticerus arambourgi, Damaliscus niro, Damaliscus sp. nov., an unnamed “spiral horn” antelope and Equus capensis), one as a mixed feeder (Taurotragus oryx) and two as browsers (Tragelaphus strepsiceros and Raphicerus melanotis). Although results from mesowear analysis sustain previous dietary classifications in the majority of cases, five species were reclassified. Three species previously classified as grazers, were reclassified as mixed feeders (H. gigas, D. aff. lunatus and R. arambourgi), one previously classified as a grazer, was reclassified as a browser (the “spiral horn” antelope), and one previously classified as a mixed feeder, was reclassified as a browser (T. oryx). While current results broadly support previous reconstructions of the Elandsfontein middle Pleistocene environment as one which included a substantial C3 grassy component, the reclassifications suggest that trees, broad-leaved bush and fynbos were probably more prominent than what was previously thought.