Final answer:
Callitrichidae, part of the Platyrrhini infraorder, are New World Monkeys distinguished by their rounded nostrils and prehensile tails, adapting to an arboreal lifestyle in Central and South America. They differ from their Old World counterparts in their arboreal nature and physical adaptations due to separate evolutionary trajectories.
Step-by-step explanation:
Understanding Callitrichidae (Platyrrhini)
The Callitrichidae family, which falls under the Platyrrhini infraorder, consists of New World Monkeys. The Platyrrhini, or platyrrhines, are primarily found in Central and South America and are notable for their round, outwardly opening nostrils and often prehensile tails, which contribute to their arboreal lifestyle. In contrast, the Catarrhini, or catarrhines, have narrow nostrils that face downwards and are located in Africa and Asia, representing the Old World monkeys, apes, and humans.
New World monkeys, such as tamarins and marmosets, tend to form pair bonds and cooperate in raising their young. Their arboreal adaptability is evident through the use of their prehensile tails which function as an additional limb for support in the trees. This feature sets them apart from their Old World counterparts, which include both arboreal and ground-dwelling species but lack prehensile tails.
The divergence between New World and Old World monkeys occurred due to continental drift, leading to different evolutionary paths and distinct adaptations. The Propliopithecoidea is believed to be the ancestor of the catarrhine primates, suggesting an African origin for New World Monkeys before their migration and isolation in the New World.