Final answer:
Australopithecine species are sorted into two categories: gracile Australopithecines, which had smaller teeth and a lighter build, and robust Australopithecines of the genus Paranthropus, which had larger teeth and were adapted to chew tough plant materials.
Step-by-step explanation:
The Australopithecine species are generally seen as belonging to one of two groups: gracile Australopithecines and robust Australopithecines. These classifications are based on physical characteristics such as morphology of the teeth and skull. The gracile species, which include Australopithecus anamensis, A. afarensis, A. africanus, and A. garhi, displayed features such as more pronounced projection of the face (prognathism), less flared cheeks without a sagittal crest, and smaller teeth and jaws. Their build suggests an adaptation to a diet of softer foods. Robust Australopithecines, classified under the genus Paranthropus, include Paranthropus robustus, P. boisei, and P. aethiopicus. These had features such as flared cheeks with a sagittal crest, which accommodated larger temporalis muscles for chewing tough plant materials, indicating a diet of coarse and fibrous vegetation.
Genus Paranthropus hominids were muscular, stood approximately 1.3 to 1.4 meters tall, and exhibited large grinding teeth that reflected their vegetarian diet. Paranthropus species went extinct over one million years ago and are an evolutionary branch that left no descendants. While gracile species emerged around 4 million years ago (MYA) and disappeared 2 MYA, robust species continued to exist for another million years before their extinction.