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?Haplorrhines[1]
Fossil range: Early Eocene – Recent
Common Squirrel Monkey (Saimiri sciureus)
Common Squirrel Monkey (Saimiri sciureus)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorrhini
Pocock, 1918
Families

Tarsiidae
Cebidae
Aotidae
Pitheciidae
Atelidae
Cercopithecidae
Hylobatidae
Hominidae

The haplorrhines, the "dry-nosed" primates (the Greek name means "simple-nosed"), are members of the Haplorrhini clade: the prosimian tarsiers and all of the true simians (the monkeys and the apes, including humans).

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 haplorrhines.

Haplorrhines are considered to be less primitive than the strepsirrhine "wet-nosed" primates (whose Greek name means "curved nose"), the other suborder of primates. The haplorrhines, 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 haplorrhine 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. Unlike the strepsirhines, haplorrhines have a post-orbital plate. Most species are diurnal (the exceptions being the tarsiers and the night monkeys) and have trichromatic color vision. Their hands and feet are more generally adapted, with specialization only for locomotion, such as the hooked hands common to gibbons and orangutans, or the human bipedal feet.

All of the simians 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, haplorrhine 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.

Classification and evolution

Haplorrhini and its sister clade, Strepsirrhini ("wet-nosed" primates), parted ways about 63 million years ago (mya). Approximately 5 million years later (58mya), 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 haplorrhines. This could explain why the prosimian tarsiers show characteristics which once caused them to be grouped with the strepsirrhines.

The remaining clade (Simiiformes [formerly 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 the Old World about 40 mya, while the apes diverged from the Old World monkeys about 25 mya. The current theory has the ape/monkey split happening in Africa. However, the recent discovery of three new anthropoid fossils (Bugtipithecus inexpectans, Phileosimias kamali and Phileosimias brahuiorum) in Pakistan's Bugti Hills is causing some scientists to revise this thinking.

In the cladist perspective of daughter groups nested within ancestral groups, humans and extinct bipedal humanoids, (including australopithecines, Kenyanthropus platyops and a few others) -are grouped together in the tribe Hominini. Hominines are classed together with knuckle-walking apes (formerly known as pongids) and are collectively referred to as great apes [Hominidae] because they each possess all the traits indicative of that clade. Similarly, all apes, large or small, living or extinct, (including humans) still share all the definitive biological traits of Haplorrhini in general, and Catarrhini specifically, and are members of each of those clades also.

References

.

  1. Groves, Colin (16 November 2005). Wilson, D. E., and Reeder, D. M. (eds) Mammal Species of the World, 3rd edition, 127-184, Johns Hopkins University Press. ISBN 0-801-88221-4.
  2. Am J Phys Anthropol. 1987 May;73(1):65-70. Vitamin C biosynthesis in prosimians: evidence for the anthropoid affinity of Tarsius. Pollock JI, Mullin RJ. [PMID 3113259]


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