ポンダウン霊長類の体重推定

抄録

This study attempted to estimate body masses for the primates from the Pondaung Formation (latest middle Eocene, central Myanmar). Because taxonomically identified materials for these possible early anthropoids are limited to dentitions, this study focused on obtaining body masses based on crown areas of cheek teeth and discussed the reliability of estimated body masses.
Body mass estimation equations were calculated using samples of 11 living prosimian species and of 30 living anthropoid species (15 platyrrhines, 13 cercopithecoids, and two Hylobates). M^1-2 and M_1-2 appeared to be better body mass estimators among cheek teeth because of their low intraspecific variations in dimensions. In addition, relatively low estimation errors for body masses derived from M_1-2 were indicated. The crown area relative to body mass differed between prosimians and anthropoids, so the body masses estimated from crown area of such teeth as P⁴ and molars referring living anthropoids became larger than those estimated referring prosimians.
The estimated body mass values for the fossils sometimes varied considerably, depending on the choices of teeth and reference taxa. Among the Pondaung primates, Bahinia seemed to better fit to the prosimian model than to the anthropoid model, but the other genera did not fit particularly better to either of the models.
The estimated body masses and ranges are as follows: Bahinia, 0.75kg (0.5 to 1.0kg); Myanmarpithecus, 1.81kg (1.5 to 2.1kg); Amphipithecus, 6.04kg (4.3 to 7.4kg); small Pondaungia, 5.33kg (4.0 to 6.6kg); and large Pondaungia, 8.56kg (7.3 to 10.1kg). Pondaungia was separable into two groups based on the size, indicating existences of two species in the sample. Pondaungia “minuta” likely belonged to the small type.