Final answer:
The unique feature of the subfamily Cercopithecinae (cercopiths) is their molar teeth, which have two parallel ridges. This adaptation is suited for their omnivorous diet and distinguishes them from other primates. They are found in the Old World and have advanced primate traits like depth perception and large brain size.
Step-by-step explanation:
Unique Characteristics of the Subfamily Cercopithecinae (Cercopiths)
The subfamily Cercopithecinae, commonly known as cheek pouch monkeys, is part of the family Cercopithecoidea and includes species that are unique among primates due to their specialized molars. Unlike other primates, the molars of the Cercopithecinae showcase two parallel ridges, adapting them for processing their omnivorous diet. These monkeys are part of the Catarrhini infraorder, which is exclusively found in the Old World regions like Africa and Asia, distinguishing them from their New World counterparts which possess a prehensile tail and different nose shapes.
Moreover, cercopiths are characterized by certain primates traits such as their reliance on touch, advanced vision with depth perception, and a large brain relative to their body size. These features are shared amongst various primate groups, indicating a complex and well-adapted evolutionary history. The clear distinction in molar structure, however, remains a defining and unique feature of the Cercopithecinae subfamily.