Final answer:
The subfamily Colobine is unique for their folivorous diet, complex stomach structure for digesting cellulose, reduced thumb, specialized molar teeth for processing tough plant fibers, and elongated limbs and non-prehensile tails adapted for arboreal living.
Step-by-step explanation:
What is unique about the subfamily Colobinae? The Colobinae are a subfamily within the larger Cercopithecoidea family, known as the leaf-eating monkeys, or colloquially, colobines. This subfamily is unique due to their adaptations for a folivorous diet, mainly consisting of leaves. The colobines have complex stomachs similar to those of ruminants, which allow them to ferment and digest cellulose from the leaves they consume. Unlike other Cercopithecoids, colobines also have a reduced thumb, aiding them in moving through the trees where they spend most of their time.
Another unique feature is their dentition; the molars of colobines are shaped to assist in the breaking down of tough plant fibers. This specialized diet distinguishes them from the cheek pouch monkeys (Cercopithecinae), which tend to have a more omnivorous diet. The Colobinae are also characterized by elongated hind limbs and tails that are not prehensile, contrasting with the New World monkeys.
Among the most well-known species within this subfamily are the langurs and proboscis monkeys, which are recognized for their distinctive appearances and behaviors that have adapted to their arboreal and leaf-eating lifestyle.