Haplorhini

Haplorhini is a suborder of Primates that comprises the dry-nosed primates, including the tarsiers (Tarsiiformes) and the simians (Simiiformes). It is one of the two major primate suborders, the other being Strepsirrhini (the wet-nosed primates such as lemurs, lorises, and galagos). Haplorhines are typically distinguished from strepsirrhines by features such as a dry nose and a greater reliance on vision over smell, as well as generally larger brain size relative to body size and more complex social behavior.

Within Haplorhini, the primary divisions are Tarsiiformes and Simiiformes. Simiiformes is commonly divided into Platyrrhini (New World monkeys) and Catarrhini (Old World monkeys and apes, including humans). Catarrhini further comprises the superfamilies Cercopithecoidea (Old World monkeys) and Hominoidea (apes and humans). This arrangement reflects major evolutionary splits within the group and their broad geographic distributions.

Notable characteristics of haplorhines include the absence of a dental comb and a higher degree of orbital closure, with many species possessing advanced color vision and forward-facing eyes. Postnatal development tends to be longer and more altricial in many lineages, contributing to complex social structures and learning. Vision is a central sensory modality for most haplorhines, with reduced reliance on olfaction compared to many strepsirrhines.

Geographic distribution varies by lineage: tarsiers are native to Southeast Asia; platyrrhines inhabit the Americas; and catarrhines are found in Africa and Eurasia. The fossil record indicates an early diversification of haplorhines in the Eocene, with the split between tarsiiforms and simians occurring early in their history.