Final answer:
Robust australopithecines had comparatively small front teeth and large back teeth, adaptations linked to their diet of tough plants and the presence of a sagittal crest which supported large jaw muscles.
Step-by-step explanation:
Compared to other hominid species, the robust australopithecines have relatively small front teeth and large back teeth. This characteristic is due to their specialized diet, which is thought to have consisted mainly of tough plant materials requiring strong and large molars for effective chewing. The sagittal crest found in robust australopithecine species catered to large temporalis jaw muscles, which highlights the adaptation of these species to their diet. Additionally, features such as large molars and decreased incisors and canines led to a flatter face with less prognathism compared to their gracile counterparts.