The australopithecines were hominids that belonged to genera Australopithecus or Paranthropus. These species occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than modern apes, lacking the encephalization characteristics of the genus Homo.
Australopithecines are classified within the Hominina subtribe of the Hominini tribe. Australopithecus appeared about 4 million years ago; Paranthropus, appeared about 2.7 million years ago. The term "Australopithecine" refers to both genera together. Australopithecus is sometimes referred to as the "gracile (slender) australopithecines", while Paranthropus are also called the "robust australopithecines".
The ancestor of the Australopithecines is the Ardipithecus genus, who lived 4.4 million years ago. The Homo genus appeared about 2.4 million years ago with Homo habilis and seems to be descended from australopithecine ancestors, more precisely from Kenyanthropus platyops branching off Australopithecus some 3.5 million years ago. An alternative possibility is the derivation of Homo directly from Ardipithecus with an as yet undiscovered link connecting Ardipithecus and Homo habilis existing in parallel to the Australopithecines in the period 4 to 2.5 million years ago.