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'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'. The phylogenetic position of extant tarsiers within the order Primates has been debated for much of the past century, and tarsiers have alternately been classified with strepsirrhine primates in the suborder Prosimii, or as the sister group to the simians (=Anthropoidea) in the infraorder Haplorrhini. Analysis of SINE insertions, a type of macromutation to the DNA, is argued to offer very persuasive evidence for the monophyly of Haplorrhini, where other lines of evidence, such as DNA sequence data, had remained ambiguous. Thus, some systematists argue that the debate is conclusively settled in favor of a monophyletic Haplorrhini.
Tarsiers have enormous eyes and long feet. Their feet have extremely elongated tarsus bones, which is how they got their name. They are primarily insectivorous, and catch insects by jumping at them. They are also known to prey on birds and snakes. As they jump from tree to tree, tarsiers can catch even birds in motion. Gestation takes about six months, and tarsiers give birth to single offspring.
All tarsier species are nocturnal in their habits, but like many nocturnal organisms some individuals may show more or less activity during the daytime. Unlike many nocturnal animals, however, tarsiers lack a light-reflecting area (tapetum lucidum) of the eye. They also have a fovea, atypical for nocturnal animals. The tarsier brain is different from other primates in terms of the arrangement of the connections between the two eyes and the lateral geniculate nucleus, which is the main region of the thalamus that receives visual information. The sequence of cellular layers receiving information from the ipsilateral (same side of the head) and contralateral (opposite side of the head) eyes in the lateral geniculate nucleus distinguishes tarsiers from lamurs, lorises and monkeys, which are all similar in this respect ^[1]. Some neuroscientists suggested that "this apparent difference distinguishes tarsiers from all other primates, reinforcing the view that they arose in an early, independent line of primate evolution" ^[2].
Fossils of tarsiers and tarsiiform primates are found in Asia, Europe, North America, and there are disputed fossils from Africa, but extant tarsiers are restricted to several Southeast Asian islands including the Philippines, Sulawesi, Borneo, and Sumatra. They also have the longest continuous fossil record of any primate genus, and the fossil record indicates that their dentition hasn't changed much, except in size, in the past 45 million years.
Tarsiers have never formed successful breeding colonies in captivity, and when caged, tarsiers have been known to injure and even kill themselves because of the stress.^[3]

Contents

Classification

Conservation status

Gallery

External links

References

Classification

★ 'Infraorder Tarsiiformes'

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★ 'Family Tarsiidae': tarsiers

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★ 'Genus ''Tarsius'''

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★ ''T. syrichta'' group

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★ Philippine Tarsier, ''Tarsius syrichta''

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★ Western or Horsfield's Tarsier, ''Tarsius bancanus''

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★ ''T. tarsier'' group

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★ Spectral Tarsier, ''Tarsius tarsier''

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★ Dian's Tarsier, ''Tarsius dentatus''

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★ Lariang Tarsier, ''Tarsius lariang''

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★ Peleng Tarsier, ''Tarsius pelengensis''

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★ Sangihe Tarsier, ''Tarsius sangirensis''

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★ Pygmy Tarsier, ''Tarsius pumilus''

Conservation status

One tarsier species, Dian's Tarsier (''Tarsius dentatus''), is listed on the IUCN Red List as being "Lower Risk - Conservation Dependent". Two other species/sub-species, Horsfield's Tarsier (''Tarsius bancanus''), ''Tarsius bancanus bancanus'', are listed as "Lower Risk - Least Concern". The Spectral Tarsier (''Tarsius spectrum'') is categorized as "Lower Risk, Not Threatened." All other tarsier species are listed as "Data Deficient".

Gallery

External links

★ Primate Info Net - Primate Factsheets & More: Tarsius sp.

★ Video of a Tarsier

★ A Synopsis of the Mammalian Fauna of the Philippine Islands

★ Tarsier behaviour: index to species

★ Descriptive Article of the Philippine Tarsier

References

1. Rosa MG, Pettigrew JD, Cooper HM (1996) Unusual pattern of retinogeniculate projections in the controversial primate Tarsius. Brain Behav Evol 48(3):121-129.
2. Collins CE, Hendrickson A, Kaas JH (2005) Overview of the visual system of Tarsius. Anat Rec A Discov Mol Cell Evol Biol 287(1):1013-1025.
3. http://web.archive.org/web/20041015083950/http://www.szgdocent.org/pp/p-tarsir.htm


;General references


★ Schmitz J, Ohme M, Zischler H (2001) SINE insertions in cladistic analyses and the phylogenetic affiliations of Tarsius bancanus to other primates. Genetics 157(2): 777-84. [1]