Final answer:
Hominoids have varied molar sizes with larger third molars in some early Homo species; cercopithecids have distinctive molars with two parallel ridges.
Step-by-step explanation:
In discussing the molar types of hominoids and cercopithecids, it is important to highlight the differences in their dental morphology. Hominoids, which include the family of great apes and humans, have varied molar sizes with the third molar being larger in some early members of the Homo genus such as australopithecines and early Homo species.
Conversely, the Cercopithecids, part of the Old-World monkey family, are characterized by having molars with two parallel ridges, adapted likely to their diet. These distinctions in dental structure support varied dietary adaptation and function, reflecting the evolutionary diversity within the primate order.