Aside from use as estimates of body mass dimorphism and fore to hind limb joint size
comparisons, postcranial elements have not often contributed to assessments of variation
in Australopithecus africanus. Meanwhile, cranial, facial, and dental size variation
is interpreted to be high or moderately high. Further, the cranial base and face express
patterns of structural (shape) variation, which are interpreted by some as evidence
for the presence of multiple species. Here, the proximal femur is used to consider
postcranial size and shape variation in A. africanus. Original fossils from Makapansgat
and Sterkfontein, and samples from Homo, Pan, Gorilla, and Pongo were measured. Size
variation was assessed by comparing the A. africanus coefficient of variation to bootstrapped
distributions of coefficient of variation samples for each taxon. Shape variation
was assessed from isometrically adjusted shape variables. First, the A. africanus
standard deviation of log transformed shape variables was compared to bootstrapped
distributions of logged standard deviations in each taxon. Second, shape variable
based Euclidean distances between fossil pairs were compared to pairwise Euclidean
distance distributions in each reference taxon. The degree of size variation in the
A. africanus proximal femur is consistent with that of a single species, and is most
comparable to Homo and Pan, lower than A. afarensis, and lower than some estimates
of cranial and dental variation. Some, but not all, shape variables show more variation
in A. africanus than in extant taxa. The degree of shape difference between some fossils
exceeds the majority of pairwise differences in the reference taxa. Proximal femoral
shape, but not size, variation is consistent with high estimates of A. africanus cranial
variation.