Species recognition and sexual dimorphism in Proconsul and Rangwapithecus

Abstract

The taxonomy of the early Miocene hominoid genera Proconsul and Rangwapithecus is re-examined. The recognition of sexual dimorphism and the identification of sex dimorphs among canine specimens is made an important element in the sorting of specimens into phena and the allocation of these to species hypodigms. I propose that specimens from Rusinga and Mfwangano previously identified as Proconsul africanus , including the well known 1948 skull, are actually females of P. nyanzae. P. africanus specimens from Songhor and the type site of Koru differ from Rusinga and Mfwangano specimens formerly placed in P. africanus . Accordingly, P. africanus sensu stricto is restricted to Koru and Songhor and Proconsul nyanzae is restricted to Rusinga and Mfwangano. Previous characterizations of P. africanus were based almost entirely upon specimens from Rusinga, and should therefore now be applied to female P. nyanzae instead; the paleobiology of P. africanus and P. nyanzae must now be reconsidered. As a result of the reassignment of the Rusinga Proconsul specimens, P. nyanzae exhibits degrees of postcanine metric variability exceeding those of living catarrhines. It is suggested that this reflects in part a true species characteristic, perhaps related to an exceptional amount of size dimorphism, and in part a preservational artifact relating to the time-accumulated nature of the fossil sample. These results have implications for the systematics of other Miocene hominoid species.