Final answer:
Australopithecines differed from apes in having relatively smaller canines. This is part of a broader trend of morphological changes that include smaller teeth and a bipedal posture, despite retaining a brain size similar to that of great apes.
Step-by-step explanation:
One feature that distinguished australopithecines from apes was relatively smaller canines. This distinction is seen in the dentition of Australopithecus afarensis, with canines and molars that were smaller when compared to those of apes but larger than those of modern humans. In addition to smaller canines, Australopithecus species shared several other characteristics with modern humans, such as bipedalism, though their brain size, relative to body mass, was more akin to great apes than modern humans.
While sexual dimorphism was more pronounced akin to modern gorillas and orangutans, with males being up to 50 percent larger than females, gracile australopithecines had smaller teeth and jaws, and no sagittal crest compared to their robust counterparts. Australopithecus species like A. africanus presented a trend towards a reduction in dentition size, indicative of their evolutionary path distinct from apes.
The distinction in dentition, particularly the size of the canines, is a clear morphological indicator that helps differentiate Australopithecus from their great ape relatives and reflects the complex evolutionary process leading to modern humans.