| Haplorhini[1] Temporal range: Early Eocene – Recent |
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|---|---|
| Common Squirrel Monkey (Saimiri sciureus) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini Pocock, 1918 |
| Families | |
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Tarsiidae |
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The haplorhines, the "dry-nosed" primates (the Greek name means "simple-nosed"), are members of the Haplorhini clade: the prosimian tarsiers and the anthropoids. The anthropoids are the catarrhines (Old World monkeys and apes, including humans) and the platyrrhines (New World monkeys).
The omomyids are an extinct group of prosimians, believed to be more closely related to the tarsiers than to any strepsirrhines, and are considered the most primitive haplorhines.
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 parted in evolution some 63 million years ago. The haplorhines, including tarsiers, have all lost the function of the terminal enzyme which manufactures vitamin C, while the strepsirrhine prosimians, like most other orders of mammals, have retained this enzyme and the ability to manufacture vitamin C.[2] 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. Their brain to body ratio is significantly greater than the strepsirrhines, and their primary sense is vision. Haplorhines have a postorbital plate, unlike the postorbital bar found in strepsirhines. 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.
Haplorhini and its sister clade, Strepsirrhini ("wet-nosed" primates), parted ways about 63 million years ago (mya). Approximately 5 million years later (58 mya), only a short time afterward from an evolutionary perspective, the infraorder Tarsiiformes, whose only remaining family is that of the tarsier (Tarsiidae), branched off from the other haplorhines. This could explain why the prosimian tarsiers show characteristics which once caused them to be grouped with the strepsirrhines.
The remaining clade ([Anthropoidea]) is divided into two parvorders: Platyrrhini (the New World monkeys) and Catarrhini (the Old World monkeys and apes). The New World monkeys split from catarrhines about 40 mya, while the apes [Hominoidea] diverged from Old World monkeys [Cercopithecoidea] about 25 mya. The available fossil evidence indicates that both the hominoid and cercopithecoid clades originated in Africa.
The following is the listing of the living Haplorrhine families, and their placement in the Order Primates:[1][3]
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