Which of the following is NOT considered a robust australopithecine?

The correct answer is Australopithecus afarensis, which is not considered a robust australopithecine. This species is classified as a gracile australopithecine, which is characterized by more slender skulls and lighter body structures compared to their robust counterparts. Robust australopithecines, such as Australopithecus aethiopicus, Australopithecus robustus, and Australopithecus boisei, are known for their more pronounced cranial features, including large teeth and strong jaws, adaptations for a diet that likely included tough, fibrous plant material.

Australopithecus afarensis, exemplified by famous fossils like "Lucy," presents a different morphological profile. It has a smaller cranial capacity, less pronounced facial features, and a body structure that suggests it was adapted for both bipedalism and climbing. This differentiation reflects evolutionary adaptations to various ecological niches and dietary sources.