Final answer:
Old World monkeys, also known as Cercopithecoidea, include species such as macaques, baboons, mandrills, and langurs. They are characterized by their narrow, downward-pointing noses, non-prehensile tails, and sometimes, the presence of ischial callosities.
Step-by-step explanation:
Examples of species in the Old World monkeys category include a diverse group known as the Cercopithecoidea, which is composed of two subfamilies: the Cercopithecinae (cheek pouch monkeys) and the Colobinae (leaf-eating monkeys). Some well-known Old World monkeys include the baboons, mandrills, macaques, and langurs.
For instance, the macaque is a widely recognized member of the Old World monkeys. One species in this genus, the rhesus macaque, has adapted to various environments, including cities where they can thrive eating human garbage. Other examples include the colorful mandrill, the large and socially complex baboon, and the various species of langurs such as the Hanuman langur. These Old World monkeys are characterized by their narrow, downward-pointing noses (a trait referred to as Catarrhini), non-prehensile tails, and in many cases, the presence of ischial callosities.
The proboscis monkey is another example of an Old World monkey, notable for its large nose and an aquatic lifestyle, with webbed fingers aiding in swimming. On the other hand, De Brazza's monkey and Allen's swamp monkey have also adapted to swamp and aquatic habitats.