Postcranial estimates of body weight in Proconsul, with a note on a distal tibia of P. major from Napak, Uganda.

A distal tibia of Proconsul major from Napak, Uganda, is described. It is morphologically similar to other Proconsul tibiae, only much larger in size. This specimen and others are used to estimate the body weight of P. major from postcrania for the first time. Body weight is predicted from articular and diaphyseal dimensions using regression equations derived from a modern comparative sample of catarrhine primates. The estimated body weight of P. major based on the Napak tibia is 86.7 kg, whereas two other P. major specimens are smaller, giving a total range of 63.4-86.7 kg and an average of 75.1 kg. The regression equations are also used to predict the body weight of specimens from Rusinga/Mfangano belonging to P. nyanzae and P. heseloni. As the body weight estimates generated here are consistent with previous postcranial-based estimates for Proconsul species, the two sets of estimates are pooled to give means of 10.9 kg for P. heseloni (n = 6) and 35.6 kg for P. nyanzae (n = 12). These findings support the traditional assignment of two species at Rusinga/Mfangano. The postcranial body weight estimates for the three species of Proconsul are compared to body weights estimated from M1 area in order to investigate possible differences in scaling between the teeth and limbs in these species. Despite being based on a smaller sample size, the postcranial estimates clearly differentiate the three taxa, whereas the dental estimates form a more continuous distribution. Molar area overestimates body weight in P. heseloni, indicating that it is megadont compared to a large sample of modern anthropoid primates. In contrast, molar area underestimates body weight in P. Nyanzae and especially P. major, suggesting relative microdonty in these taxa.