The skull of Proconsul africanus: reconstruction and cranial capacity

Abstract

The distorted skull of a female Proconsul africanus was found by Dr M. Leakey in 1948 in early Miocene sediments at locality R106 on Rusinga Island, Kenya1,2. Le Gros Clark1 and Robinson3 both made graphic reconstructions of this skull showing significant prognathism. The occipital portion of the skull could not, however, be attached to the main specimen because large posterior parts of the skull were missing. Two pieces missing from this skull have now been found, and these make it possible to attach the main specimen to the occipital portion. The skull is now complete in the midline from the face to the foramen magnum. The skull is distorted, but arc measurements along the midline are still accurate. A regression analysis of these arcs and cranial capacities in recent catarrhines allows us to make an accurate cranial capacity estimate for P. africanus for the first time. It seems that P. africanus had a relatively larger brain than extant monkeys of similar body size. The new pieces also make possible a more complete reconstruction.