Prosimian

The Ring-tailed Lemur (Lemur catta) is a prosimian of the family Lemuridae.

Prosimian is an informal grouping of primates consisting of those belonging to the Primates suborder Strepsirrhini and the tarsiers of the suborder Haplorrhini. At one point, all prosimians comprised the taxon Prosimii, but this grouping was determined to be polyphyletic.

Prosimians include the lemurs, lorises, galagos, and the Aye-aye of Strepsirrhini and the tarsiers of Haplorrhini. Prosimians are considered the most primitive extant primates, with characteristics similar to forms that were ancestral to monkeys, apes and humans. Prosimians are the only primates native to Madagascar, and are also found in Southeast Asia.

Overview and description

The mammalian order Primates is divided informally into three main groupings: prosimians, monkeys of the New World, and monkeys and apes of the Old World. The prosimians are species whose bodies most closely resemble that of the early proto-primates.

Early classification schemes broke the primate order into the suborders Prosimii (prosimians) and Anthropoidea (simians—monkeys and apes). However the prosimian tarsiers have been shown to be more closely related to the simians, and so it has been moved into the Anthropoidea, which is now renamed as Haplorrhini and Prosimii renamed as Strepsirrhini. Thus, present day taxonomies have the primates divided into the suborder Strepsirrhini, with all prosimians except the tarsiers, and suborder Haplorrhini, with the tarsiers, monkeys, and apes.

Well-known extant prosimians include lemurs, the Aye-aye, bushbabies (galagos), and tarsiers. The adapids are an extinct grouping that were most certainly prosimians and closely related to the strepsirhines. The omomyids are another extinct group of prosimians but they are believed to be haplorrhines, closely related to the tarsiers, but an outgroup to the rest of the haplorrhines.

Strepsirrhini

All prosimians except the tarsiers are members of the taxon Strepsirrhini, which is one of the two suborders of primates.

One of the most distinguishing characteristic of these primates is their "wet noses." The Greek name means having a curved or bent nose (a terpsimbrotos compound of strepho or "bend" and rhis or "nose"). The rhinarium' is the wet, naked surface around the nostrils of the nose, such as found in most mammals. Primates are phylogenetically divided into Strepsirrhini ("curly-nosed" primates with rhinariums) and Haplorrhini ("simple-nosed" primates that have a more mobile, continuous, dry upper lip instead of the rhinarium). Mammals with rhinariums tend to have a stronger sense of olfaction, and the loss of the rhinarium in the haplorrhine primates is related to their decreased reliance on olfaction, being associated with other derived characteristics such as a reduced number of turbinates.

Madagascar's only primates (apart from humans) are strepsirrhines, although others can be found in southeast Asia and Africa.

The suborder Strepsirrhini is composed of seven families and includes four families of creatures typically called lemurs, and three families with the lorises, pottos, galagos, and Aye-aye.

Strepsirrhines are considered to have more primitive features and adaptations than their haplorrhine cousins. Their moist nose is connected to the upper lip, which is connected to the gum, giving them a limit to the facial expressions they can manage. Their brain to body ratio tends to be smaller, indicating a lower intelligence. Their brain's olfactory lobes are larger, lending to the notion that they have a stronger reliance on smell. Their snouts are generally elongated giving them a dog-like appearance, although this is true of some monkeys, too. Strepsirrhines also have a post-orbital bar, adding to the primitive nature when compared to the suborder Haplorrhini. The strepsirrhines have also retained the ability to enzymatically manufacture vitamin C, which has been lost by all the haplorrhines, including the tarsidae (Pollock and Mullin 1987).

With the exception of the Aye-aye, all strepsirrhines have a toothcomb—tightly clustered incisors and canine teeth—that is used for grooming. Another grooming adaptation is a claw on the second toe of all strepsirrhines, while the big toe is widely separated from the others allowing a vise-like grip for locomotion.

About 75% of species are nocturnal and all of these have a tapetum, a shiny, reflective layer in the back of their eyes, although several diurnal species like the Ring-tailed Lemur have it as well. Many of the nocturnal species also have very sensitive hearing and ears they can move independently to capture sounds even better.

Strepsirrhine reproduction differs greatly from haplorrhine reproduction. Instead of an individual cycle, strepsirrhines have a breeding season. They also have a litter of offspring and the females have a Y-shaped (bicornate) uterus and multiple sets of nipples.

Tarsiers

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). 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. 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 th

Tarsiers are prosimian primates of the genus Tarsius, a monotypic genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes. Although the group was once more widespread, all the species living today are found in the islands of Southeast Asia.

Description

Tarsiers are small animals with enormous eyes and very long hind limbs. Their feet have extremely elongated tarsus bones, from which the animals get their name. The head and body range from 10 to 15 cm in length, but the hind limbs are about twice this long (including the feet), and they also have a slender tail from 20 to 25 cm long. Their fingers are also elongated, with the third finger being about the same length as the upper arm. Most of the digits have nails, but the second and third toes of the hind feet bear claws instead, which are used for grooming. Tarsiers have very soft, velvety fur, which is generally buff, beige, or ochre in color.

Unlike other prosimians, tarsiers have no tooth-comb, and their dental formula is also unique:

2.1.3.3

1.1.3.3

Classification

The prosimians were once considered a suborder of the Primate order (suborder Prosimii)(Gr. pro, before, + simia, ape). They have been shown, however, to be paraphyletic - that is, the smallest clade of related species that includes all of the prosimians also includes other species - in this case all of the primates.This relationship is shown by the ranks (prosimians in bold) in the list below of the current Primate classification between the order and family level. The classification is used on a more behavioural term nowadays, due to the lack of a unique last common ancestor.

• ORDER PRIMATES
  • Suborder Strepsirrhini: non-tarsier prosimians
    • Infraorder Lemuriformes
      • Superfamily Cheirogaleoidea
        • Family Cheirogaleidae: dwarf lemurs and mouse-lemurs
      • Superfamily Lemuroidea
        • Family Lemuridae: lemurs
        • Family Lepilemuridae: sportive lemurs
        • Family Indriidae: woolly lemurs and allies
    • Infraorder Chiromyiformes
      • Family Daubentoniidae: Aye-aye
    • Infraorder Lorisiformes
      • Family Lorisidae: lorises, pottos and allies
      • Family Galagidae: galagos
  • Suborder Haplorrhini: tarsiers, monkeys and apes
    • Infraorder Tarsiiformes
      • Family Tarsiidae: tarsiers
    • Infraorder Simiiformes
      • Parvorder Platyrrhini: New World monkeys (4 families)
      • Parvorder Catarrhini: humans and other Old World primates (3 families)

References

ISBN links support NWE through referral fees

Smithsonian National Zoological Park (SNZP). 2008. http://nationalzoo.si.edu/Animals/Primates/Facts/Primateness/Differences/ Great apes and other primates: Differences among prosimians, monkeys and apes

.

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Prosimian  ^history
• Strepsirrhini  ^history
• Haplorrhini  ^history
• Tarsier  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Prosimian"

Note: Some restrictions may apply to use of individual images which are separately licensed.