What key anatomical feature distinguishes the New World monkey suborder Platyrrhini?

Wide, flat noses

The classification of New World monkeys into the suborder *Platyrrhini* is directly tied to their physical morphology, specifically the structure of their nose. The term Platyrrhini itself describes this characteristic, meaning 'flat nose.' This anatomical feature is a primary differentiator when comparing them to Old World monkeys, classified under *Catarrhini*, whose nostrils are oriented downward. This difference in skeletal structure reflects millions of years of separate evolutionary development following the split between these two major primate groups. The structure of the nose influences facial appearance and is a consistent marker used in primate taxonomy to separate New World species originating from the Americas from those originating in Africa and Asia.