Final answer:
No, it is false that all Australopithecines had a robust sagittal crest. Only the robust Australopithecines had this feature, while gracile Australopithecines did not.
Step-by-step explanation:
The statement that all of the Australopithecines had a robust sagittal crest is false. Australopithecines are divided into two classifications based on their physical characteristics: gracile and robust forms. Gracile Australopithecines, which include species like Australopithecus anamensis, A. afarensis, A. africanus, A. garhi, and A. sediba, did not have a sagittal crest and had smaller teeth and jaws. Meanwhile, robust Australopithecines, which fall under the genus Paranthropus and include species such as Paranthropus robustus, P. boisei, and P. aethiopicus, did feature a prominent sagittal crest to accommodate large chewing muscles for their tough plant-based diet.