The members of the genus Australopithecus--Australopithecines--are supposed by researchers to be the first common ancestor of apes and men, and they are the evolutionary step before the genus Homo.

The "robust" in robust Australopithecines refers not to the body, but to the jaws. Robust Australopithecines developed _gigantic_ teeth and jaws for the purposes of chomping down roots and fibers. To accomodate such gigantic jaws, they needed more muscle, so they evolved this thing called a sagittal crest to offer more surface area on the skull for muscle. They also had a fairly pronounced sexual dimorphism

Some species that were robust Australopithecines include Australopithecus robustus and Australopithecus boisei. Robust Australopithecines are thought to have ultimately gone extinct, being an evolutionary dead end. Some researchers have suggested moving them into a new genus to mark their divergence from the other Australopitheceans (called gracile Australopithecines), which had more delicate features, sharper teeth, and ultimately evolved into modern apes and men.