New Postcranial Fossils of Proconsul africanus and Proconsul nyanzae

Abstract

Our understanding of early Miocene hominoid postcranial material has been built upon a fossil record that consists, for the most part, of unassociated fragments of different individuals from different sites. Although many skeletal parts have been known from small to large Proconsul species, major problems have arisen due to lack of knowledge of limb proportions and to difficulties in assigning postcrania to species based on teeth and jaws. Because of this our viewpoint has been heavily biased by interpretations based on the associated partial skeleton of P. africanus (Napier and Davis, 1959). Recently two things happened to change this situation. The first was the recognition that more parts of the associated skeleton, KNM-RU 2036, were still in blocks of matrix in the National Museums of Kenya and that more are likely still to be on the site, locality R114, Rusinga Island. This has led to the recognition of many more parts of this individual and their preparation from their matrix. Importantly, much of the hindlimb skeleton is now known. The second was the finding of the major part of an associated foot and leg skeleton that can be reasonably attributed to P. nyanzae at site R1–3, Rusinga Island. These new finds allow us to do several things:

• 1. The limb proportions of P. africanus can be almost perfectly calculated for one individual.

• 2. The estimate of body weight for this individual is now on a much sounder foundation than before.

• 3. The hypotheses concerning locomotor adaptations that were based on the forelimb can now be checked against the hindlimb.

• 4. The body weight of P. nyanzae can be estimated, based on the size of the leg and foot skeleton and other reasonably attributed parts.

• 5. Comparisons can be made between the two species.