AUSTRALOPITHECINES — ROBINSON 481 



much in fact that it is my opinion that there is a far more fundamental 

 split within the australopithecine group than there is between one 

 of these subgroups {Australopithecus) and the hominines. That is 

 to say, that if one has to divide the known hominids into two groups 

 only, there is a good case for putting part of the australopithecine 

 group (Aiostralopithecus) with the hominines as one group and leaving 

 the other australopithecine subgroup {Paranthropus) as the second 

 group. 



Two different forms of australopithecine are known in South Africa 

 at present. Australopithecus occurs at Taung, Sterkfontein, and 

 Makapansgat Limeworks, while Paranthropus has been found at 

 Kromdraai and Swartkrans. It is important to realize that the largest 

 Paranthropus sample (160 specimens from Swartkrans) occurs less 

 than a mile from Sterkfontein, which yielded the largest sample of 

 Australopithecus (108 specimens). Geographic variation can there- 

 fore be disregarded as an explanation of differences between the 

 groups. Apparently the time difference between these two sites is not 

 great, and since Paranthropus apparently occurs both much earlier 

 and later in time without any significant difference in its morphology, 

 one can virtually eliminate the effect of time differences as well as of 

 geographical differences. One is thus in an exceptionally favorable 

 position to assess the nature of the differences between the two popu- 

 lation samples. 



Australopithecus has a dolichocephalic skull with a good hominine 

 shape. A distinct low forehead is present, and the vertex rises well 

 above the level of the brow ridges. The latter are poorly developed, 

 and the postorbital constriction is moderately developed. The face 

 is fairly wide, the nasal region is slightly raised above the surrounding 

 level of the face, which is distinctly prognathous. The skull is gracile 

 without any heavy bone or strong development of ridges or crests. 

 The mandible is robust with a moderately high ramus and an almost 

 vertical chin region. The dentition is morphologically very similar to 

 that of the early hominines. Molars and premolars are very well 

 developed, and the canines are fairly large but do not protrude because 

 they are recessed into the jaw to a greater extent than the other 

 teeth. The proportions along the tooth row are typical of early 

 hominines. 



Paranthropus is very different. Although the endocranial volume 

 appears to differ insignificantly from that of Australopithecus, the 

 skull architecture is markedly dissimilar. The skull is brachycephalic 

 with no trace of a forehead ; the frontal passes straight back from the 

 well-developed supraorbital torus in a manner reminiscent of the 

 condition in the gorilla. The vertex rises very little above the upper 

 level of the orbits. Le Gros Clark (1955) devised an index to measure 



