Simiiformes

Simiiformes is an infraorder of primates that includes monkeys, apes, and humans. The term "simian" is often used interchangeably with monkey or ape. These primates are characterized by their relatively large brains, forward-facing eyes, and grasping hands and feet.12

There are two main groups of monkeys: Old World monkeys (catarrhines) and New World monkeys (platyrrhines). Old World monkeys, found in Africa and Asia, have narrow noses with downward-facing nostrils and lack prehensile tails. New World monkeys, found in the Americas, have broad noses with outward-facing nostrils, and many species possess prehensile tails. Apes and humans are also considered simians, distinguished from monkeys by their lack of tails and other skeletal features.2