catarrhine

Catarrhini is a parvorder of primates that includes the Old World monkeys (Cercopithecoidea) and the apes (Hominoidea), a group that also comprises humans. The name derives from the Greek katarrhinos, meaning downward-nostriled, referring to the orientation of the nostrils that distinguishes catarrhines from New World monkeys (Platyrrhini).

Catarrhines are characterized by a dental formula of 2.1.2.3 for both upper and lower jaws and a fully enclosed bony orbit, known as postorbital closure. They typically have non-prehensile tails, though tails vary by lineage, and many apes lack tails entirely. The two subgroups show considerable diversity in size and habitat, ranging from arboreal to terrestrial species.

In the traditional taxonomy, Catarrhini is divided into Cercopithecoidea (Old World monkeys) and Hominoidea (apes, including humans). The split between catarrhines and platyrrhines is thought to have occurred in the late Paleocene or early Eocene, roughly 40 million years ago, with fossils and molecular data placing major diversification in Africa and Asia. Present-day catarrhines inhabit Africa and Asia, with humans having a worldwide distribution, while Old World monkeys are found in Africa and Asia and apes in Africa and Asia. The group exhibits a wide range of social structures and locomotor adaptations.