Final answer:
Robust australopithecines are characterized by a flared zygomatic arch suggesting strong cheeks, and later synapsids possess anatomical features such as a zygomatic arch and a secondary palate supporting the presence of cheeks for food processing.
Step-by-step explanation:
The question refers to evidence for the presence of cheeks in a specific clade. In the context of paleoanthropological findings, evidence for the presence of cheeks in early hominins and synapsids can be inferred from the skeletal structure of the skull, particularly the zygomatic arch. The robust australopithecines, such as Paranthropus robustus, are characterized by a flared zygomatic arch that indicates the presence of large temporalis muscles for chewing. This flared zygomatic arch and accompanying sagittal crest suggest that robust australopithecines had strong cheeks needed for mastication of tough plant materials. Additionally, in later synapsids which are closer to mammals, the existence of cheeks is also suggested by the presence of the zygomatic arch, the ability to chew and breathe simultaneously due to a secondary palate, and heterodont teeth, which are specialized for the mechanical processing of food.