Final answer:
The sagittal crest is a bony ridge on the skull that allows for the attachment of large jaw muscles, aiding in the chewing of tough plant materials. Robust australopithecines are an example of primates with this feature.
Step-by-step explanation:
The sagittal crest is a bony ridge on the top of the skull to which the jaw muscles are attached. It is found in some species of primates and other animals. The purpose of the sagittal crest is to provide additional surface area for the attachment of large temporalis muscles, which are important for chewing tough plant materials. An example of a primate with this feature is the robust australopithecines, a group that exhibits strong sagittal crests due to their diet requiring significant chewing power.