Ecomorphology and Behavior of Giant Extinct Lemurs from Madagascar

Data are presented on adult body mass for 230 of 249 primate species, based on a review of the literature and previously unpublished data. The issues involved in collecting data on adult body mass are discussed, including the definition of adults, the effects of habitat and pregnancy, the strategy for pooling data on single species from multiple studies, and use of an appropriate number of significant figures. An analysis of variability in body mass indicates that the coefficient of variation for body mass increases with increasing species mean mass. Evaluation of several previous body mass reviews reveals a number of shortcomings with data that have been used often in comparative studies.

The postcranial skeleton of Australopithecus afarensis from the Hadar Formation, Ethiopia, and the footprints from the Laetoli Beds of northern Tanzania, are analyzed with the goal of determining (1) the extent to which this ancient hominid practiced forms of locomotion other than terrestrial bipedality, and (2) whether or not the terrestrial bipedalism of A. afarensis was notably different from that of modern humans. It is demonstrated that A. afarensis possessed anatomic characteristics that indicate a significant adaptation for movement in the trees. Other structural features point to a mode of terrestrial bipedality that involved less extension at the hip and knee than occurs in modern humans, and only limited transfer of weight onto the medial part of the ball of the foot, but such conclusions remain more tentative than that asserting substantive arboreality. A comparison of the specimens representing smaller individuals, presumably female, to those of larger individuals, presumably male, suggests sexual differences in locomotor behavior linked to marked size dimorphism. The males were probably less arboreal and engaged more frequently in terrestrial bipedalism. In our opinion, A. afarensis from Hadar is very close to what can be called a "missing link." We speculate that earlier representatives of the A. afarensis lineage will present not a combination of arboreal and bipedal traits, but rather the anatomy of a generalized ape.

Measurements were taken on the upper and lower molars of 37 species of primates and one tupaiid to assess the relative importance of shearing, crushing and grinding features. Significant correlations were found between pairs of allometrically standardized dimensions which measure the same molar function (shearing, crushing, or grinding). Correlations between pairs of dimensions which do not measure the same function are not significant. Second molar adaptations for shearing, crushing, and grinding, as well as the length of the second lower molar, and the total surface of the post-canine dentition are negatively allometric with respect to metabolic rate. Species which take different proportions of fruit, leaves, and insects in their diets have different molar structure. Frugivores have small teeth for their adult body size with poorly developed shearing, crushing, and grinding features on their molars. By contrast, leaf-eating species tend to have large teeth for their adult body size with well developed shearing, crushing, and grinding. The second molars of insectivorous species were found to parallel closely those of leaf-eating species. The two groups are clearly distinguishable from the former on the basis of body size alone: the smallest living primate leaf-eater is on order of magnitude larger than the largest living primate insectivore.