platyrrhines

Platyrrhines, or New World monkeys, are a clade of haplorhine primates that inhabit tropical and subtropical forests of Central and South America, ranging from southern Mexico to northern Argentina. They are distinguished from Old World monkeys by their broad, outward-facing noses with widely spaced nostrils, hence the name platyrrhine. They are generally arboreal and rely on grasping hands and feet for locomotion, with diets that vary from fruit and seeds to leaves and insects. Most species have a dental formula of 2.1.3.3.

Extant platyrrhines are divided into five families: Callitrichidae (marmosets and tamarins), Cebidae (capuchins and squirrel monkeys), Pitheciidae (titis, sakis, and uakaris), Atelidae (howler, spider, and woolly monkeys), and Aotidae (night monkeys). A key morphological distinction is that many Atelidae possess a prehensile tail that functions as a sixth limb for grasping branches, a feature not found in the other families. Social structures are diverse, ranging from pair-bonds in some species to large, multimale–multifemale groups, and cooperative breeding is common in Callitrichidae.

Fossil and molecular evidence indicate that platyrrhines diverged from the Catarrhini lineage in the early Cenozoic, with the New World lineage established in South America by the Oligocene. The earliest definite New World monkey fossils include Branisella boliviana from Bolivia (about 26 million years ago). The modern diversity arose within the Neotropics, shaped by isolation and ecological radiation in forest habitats.

Conservation concerns are prominent, as many platyrrhine species face threats from deforestation, habitat fragmentation, and hunting. IUCN assessments vary by species, with several listed as threatened, highlighting the need for habitat protection and continued research.