Final answer:
Early Australopithecus forms had smaller, ape-like skulls with a sloped forehead, larger teeth, and a prominent jaw, coupled with long arms and curved digits for tree-climbing, while featuring a human-like pelvis for bipedal locomotion.
Step-by-step explanation:
The early forms of Australopithecus, such as Australopithecus afarensis and Australopithecus africanus, exhibit a combination of ape-like and human-like features. These hominids had smaller skulls compared to modern humans, with a sloped forehead, larger teeth, and a prominent jaw. The brain size of A. afarensis was around 400cc, similar to that of a common chimpanzee, while A. africanus had a slightly larger brain at 500cc. They had long arms and curved finger and toe bones, appropriate for climbing trees, yet their pelvis shape indicates that they were adapted for bipedal walking. The gracile species like A. africanus had a slender build, while robust species had larger jaws and teeth designed for processing tough plant materials.