Haplorhini

Haplorhines Temporal range: Paleocene-Holocene PreꞒ Ꞓ O S D C P T J K Pg N
Hamadryas baboon (Papio hamadryas)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Suborder:	Haplorhini Pocock, 1918[1]
Infraorders
Simiiformes (monkeys and apes) Tarsiiformes (tarsiers) sister: Strepsirrhini
Synonyms
Simia

Haplorhini (/hæpləˈraɪnaɪ/), the haplorhines (Greek for "simple-nosed") or the "dry-nosed" primates is a suborder of primates containing the tarsiers and the simians (Simiiformes or anthropoids), as sister of the Strepsirrhini ("moist-nosed"). The name is sometimes spelled Haplorrhini.^[2] The simians include catarrhines (Old World monkeys and apes, including humans), and the platyrrhines (New World monkeys).

Haplorhini was proposed by Pocock in 1918 when he realized the tarsiers were actually sister to the monkeys rather than the lemurs, also following findings of Hugh Cuming 80 years earlier and Linnaeus 160 years earlier.^[1][3] For Linnaeus, this ensemble of primates constituted a genus "Simia". For religious reasons, Homo constituted its own genus (which has remained).^{[citation needed]}

The extinct omomyids, which are considered to be the most basal haplorhines, are believed to be more closely related to the tarsiers than to other haplorhines. The exact relationship is not yet fully established – Williams, Kay and Kirk (2010) prefer the view that tarsiers and simians share a common ancestor, and that common ancestor shares a common ancestor with the omomyids, citing evidence from analysis by Bajpal et al. in 2008; but they also note two other possibilities – that tarsiers are directly descended from omomyids, with simians being a separate line, or that both simians and tarsiers are descended from omomyids.^[4]

Haplorhines share a number of derived features that distinguish them from the strepsirrhine "wet-nosed" primates (whose Greek name means "curved nose"), the other suborder of primates from which they diverged some 63 million years ago^{[citation needed]}. The haplorhines, including tarsiers, have all lost the function of the terminal enzyme that manufactures Vitamin C, while the strepsirrhines, like most other orders of mammals, have retained this enzyme.^[5] Genetically, five short interspersed nuclear elements (SINEs) are common to all haplorhines whilst absent in strepsirrhines.^[4] The haplorhine upper lip, which has replaced the ancestral rhinarium found in strepsirrhines, is not directly connected to their nose or gum, allowing a large range of facial expressions.^[6] Their brain-to-body mass ratio is significantly greater than the strepsirrhines, and their primary sense is vision. Haplorhines have a postorbital plate, unlike the postorbital bar found in strepsirrhines. Most species are diurnal (the exceptions being the tarsiers and the night monkeys).

All anthropoids have a single-chambered uterus; tarsiers have a bicornate uterus like the strepsirrhines. Most species typically have single births, although twins and triplets are common for marmosets and tamarins. Despite similar gestation periods, haplorhine newborns are relatively much larger than strepsirrhine newborns, but have a longer dependence period on their mother. This difference in size and dependence is credited to the increased complexity of their behavior and natural history.^[7]