View source for Prosimian

{{Short description|Obsolete primate taxon}}
{{Paraphyletic group
| name = Prosimian
| fossil_range = {{Geological range|Early Eocene|Present|earliest=Early Paleocene}}
| image = Tarsius syrichta03.jpg
| image_caption = [[Tarsier]]s are prosimian primates, but more closely related to monkeys and apes ([[simian]]s) than to other prosimians.
| auto = yes
| taxon = Prosimii
| authority = [[Johann Karl Wilhelm Illiger|Illiger]], 1811{{efn|The division of the order Primates into two [[evolutionary grade]]s, Prosimii ("lower primates") and Anthropoidea ("higher primates") is sometimes used, but has been shown through morphological and genetic evidence to be incorrect. Alternatively, a three-way split in the order Primates—Prosimii, Tarsiiformes, and Anthropoidea—has also been suggested.{{Sfn|Rose|2006|p=166}}}}
| includes =
:[[Strepsirrhini]]{{efn|name=Lemuriformes|Although the [[Monophyly|monophyletic relationship]] between lemurs and lorisoids is widely accepted, their clade name is not. The term "lemuriform" is used here because it derives from one popular taxonomy that clumps the [[clade]] of toothcombed primates into one [[Taxonomic rank|infraorder]] and the extinct, non-toothcombed [[Adapiformes|adapiforms]] into another, both within the [[Taxonomic rank|suborder]] Strepsirrhini.{{Sfn|Szalay|Delson|1980|p=149}}{{Sfn|Cartmill|2010|p=15}} However, another popular alternative taxonomy places the [[Lorisoidea|lorisoids]] in their own infraorder, Lorisiformes.{{Sfn|Hartwig|2011|pp=20–21}}}}
:[[Tarsiiformes]]
| excludes=
[[Simiiformes]]
}}

'''Prosimians''' are a group of [[primate]]s that includes all living and extinct [[Strepsirrhini|strepsirrhines]] ([[lemur]]s, [[Lorisoidea|lorisoids]], and [[Adapiformes|adapiforms]]),<ref name="WhittenBrockman2001" /> as well as the [[Haplorhini|haplorhine]] [[tarsier]]s and their extinct relatives, the [[Omomyidae|omomyiforms]], i.e. all primates excluding the [[simians]]. They are considered to have characteristics that are more "[[Primitive (biology)|primitive]]" (ancestral or [[Cladistics#Terminology for character states|plesiomorphic]]) than those of [[simian]]s (monkeys, apes, and humans).<ref name="WhittenBrockman2001">{{cite book | last1 = Whitten | first1 = P. L. | last2 = Brockman | first2 = D. K. | year = 2001 | chapter = Chapter 14: Strepsirrhine reproductive ecology | pages = 321–350 | editor1-last = Ellison | editor1-first = P. T | title = Reproductive Ecology and Human Evolution | publisher = Transaction Publishers | isbn = 978-0-202-30658-2 | chapter-url = https://books.google.com/books?id=M4VJ5ee_1YoC&pg=PA321}}</ref>

[[Simian]]s emerged within the Prosimians as sister group of the [[Haplorhini|haplorhine]] [[tarsier]]s, and therefore [[Cladistics|cladistically]] belong to this group. Simians are thus distinctly closer related to tarsiers than lemurs are. Strepsirrhines bifurcated some 20 million years earlier than the tarsier–simian bifurcation. However, simians are traditionally excluded, rendering prosimians [[paraphyletic]]. Consequently, the term "prosimian" is no longer widely used in a taxonomic sense, but is still used to illustrate the behavioral ecology of tarsiers relative to the other primates.

Prosimians are the only primates native to [[Madagascar]], but are also found throughout Africa and in Asia.

==Characteristics==
[[Image:GarnettsGalago CincinnatiZoo.jpg|thumb|The [[tapetum lucidum]] of a [[galago]], typical of prosimians, reflects the light of the photographer's flash.]]
Being an [[evolutionary grade]] rather than a [[clade]], the prosimians are united by being primates with traits otherwise found in non-primate mammals. Their diets typically are less dominated by fruit than those of the simians, and many are active arboreal predators, hunting for insects and other small animals in the trees.<ref name="WhittenBrockman2001"/> All prosimians outside Madagascar are [[nocturnal]], meaning that no prosimian competes directly with simian primates (the only nocturnal simians are [[New World monkey]]s of genus ''[[Aotus (monkey)|Aotus]]''<ref name=Lang>Cawthon Lang KA. 2005 July 18. [http://pin.primate.wisc.edu/factsheets/entry/owl_monkey/taxon Primate Factsheets: Owl monkey (''Aotus'') Taxonomy, Morphology, & Ecology]. Accessed 2012 July 25.</ref>).

Related to their frequently nocturnal lifestyle, prosimians lack the colour vision of higher primates. Like most [[Placentalia|placental mammals]], they are in effect [[Color blindness#Red–green color blindness|red–green colour blind]]. This allows for more [[rod cell]]s in the [[retina]], which may enhance vision under low-light conditions.<ref name=Ali&Klyne1985>{{Cite book|last1=Ali|first1=Mohamed Ather|last2=Klyne|first2=M.A.|title=Vision in Vertebrates|place=New York|publisher=Plenum Press|year=1985|pages=174–175|isbn=978-0-306-42065-8}}</ref> Except in tarsiers, the nocturnal vision is further augmented by a reflective [[tapetum lucidum]] behind the retina, similar to that found in other nocturnal mammals. This layer reflects the light that passes through the retina, increasing the [[Photoreceptor cell|photoreceptors]] exposure to the light. It is however not well developed in diurnal forms like many lemurs.<ref>{{cite journal|last=Pariente|first=GF|title=[Different aspects of the limit of the tapetum lucidum in prosimians]|journal=Vision Research|date=1976|volume=16|issue=4|pages=387–91|pmid=821249|doi=10.1016/0042-6989(76)90201-7|s2cid=53156761}}</ref>

All prosimians possess two laterally flattened [[toilet claw]]s, used for grooming. These are found on the second toe in [[lemurs]] and [[lorises]], and the second and third in [[tarsiers]]. [[Aye-aye]]s have functional [[claw]]s on all other digits except the hallux, including a toilet claw on the second toe. Clawlike nails are however also found in the small-bodied [[callitrichids]], a group of New World monkeys, though none of them have a toilet claw.<ref name=evolution>{{cite journal |author=Soligo, C. |author2=Müller, A.E. |year=1999 |title=Nails and claws in primate evolution |journal=Journal of Human Evolution |volume=36 |pages=97–114 |doi=10.1006/jhev.1998.0263 |pmid=9924135 |issue=1}}</ref>

Male strepsirrhine prosimians have relatively large [[Baculum|bacula]].<ref>{{Cite book |last=Ankel-Simons |first=Friderun |url=https://www.google.com/books/edition/Primate_Anatomy/Mwl3M6c5KzoC?hl=en&gbpv=1&pg=PA521&printsec=frontcover&dq=baculum |title=Primate Anatomy: An Introduction |date=2010-07-27 |publisher=Elsevier |isbn=978-0-08-046911-9 |language=en}}</ref> Male tarsiers do not have [[baculum|bacula]].<ref name="Ankel-Simons2010">{{cite book|author=Friderun Ankel-Simons|title=Primate Anatomy: An Introduction|url=https://books.google.com/books?id=Mwl3M6c5KzoC|date=27 July 2010|publisher=Academic Press|isbn=978-0-08-046911-9|pages=442, 521 }}</ref> The prosimians have retained the primitive mammalian condition of a [[bicornuate uterus]], with two separate uterus chambers. In the simians, the uterus chambers have fused, an otherwise rare condition among mammals. Prosimians usually have litters rather than single offspring, which is the norm in higher primates.<ref>{{cite book |last=Nowak |first=Ronald M. |title=Walker's primates of the world |year=1999 |publisher=Johns Hopkins University Press |location=Baltimore |isbn=978-0801862519 |page=[https://archive.org/details/walkersprimateso0000nowa/page/25 25] |url=https://archive.org/details/walkersprimateso0000nowa|url-access=registration |quote=prosimians uterus placenta. }}</ref>

While primates are often thought of as fairly intelligent animals, the prosimians are not very large-brained compared to other placental mammals. Their brain-cases are markedly smaller than those of simians of comparable sizes. In the large-eyed tarsiers, the weight of the brain is about the same as that of a single eye.<ref>{{cite journal|last=Rosenberger|first=Alfred L.|title=The Skull of Tarsius: Functional Morphology, Eyeballs, and the Nonpursuit Predatory Lifestyle|journal=International Journal of Primatology|date=16 October 2010|volume=31|issue=6|pages=1032–1054|doi=10.1007/s10764-010-9447-x|s2cid=3905636}}</ref> Prosimians generally show lower cognitive ability and live in simpler social settings than the simians. The prosimians with the most complex social systems are the diurnal lemurs, which may live in social groups of 20 individuals. The nocturnal prosimians are mainly solitary.<ref name="Reader">{{Cite journal | last = Reader | first = S. M. | author2 = Hager, Y. | author3 = Laland, K. N. | title = The evolution of primate general and cultural intelligence | journal = [[Philosophical Transactions of the Royal Society B: Biological Sciences]] | volume = 366 | issue = 1567 | pages = 1017–1027 | date = 2011-04-12 | url = http://lalandlab.st-andrews.ac.uk/pdf/Publication163.pdf | doi = 10.1098/rstb.2010.0342 | pmid = 21357224 | access-date = 2011-07-04 | url-status = dead | archive-url = https://web.archive.org/web/20111003152030/http://lalandlab.st-andrews.ac.uk/pdf/Publication163.pdf | archive-date = 2011-10-03 | pmc = 3049098 }}</ref>

==Classification==
{{cladogram|title=Primate phylogeny{{Sfn|Rose|2006|pp=}}
|caption=Prosimians (in <span style="color:green;">green</span> brackets) are a [[Paraphyly|paraphyletic group]] by including the tarsiers and omomyiforms to the exclusion of the simians (in <span style="color:red;">red</span> brackets).
|clades={{Barlabel|style=font-size:90%;width:520px;|labelwidth=5.5
|size=8
|at1=3|label1=prosimians|bar1=green
|at2=7|label2=simians|bar2=red
|cladogram=
{{Clade
|label1=Primates
|1={{Clade
   |label1=Strepsirrhini
   |1={{Clade
      |label1=Adapiformes
      |1={{extinct}}Adapiforms|barbegin1=green
      |label2=Lemuriformes
      |2={{Clade
         |1=Lemurs|bar1=green
         |2=Lorisoids|bar2=green
         }}
      }}
   |label2=Haplorhini
   |2={{Clade
      |label1=Omomyiformes
      |1={{extinct}}Omomyiforms|state1=dashed|bar1=green
      |label2=Tarsiiformes
      |2=Tarsiers|barend2=green
      |label3=Simiiformes
      |3={{Clade
         |label1=Platyrrhini
         |1=New World monkeys|barbegin1=red
         |label2=Catarrhini
         |2={{Clade
            |1=Old World monkeys|bar1=red
            |2=Apes & humans|barend2=red
            }}
         }}

      }}

   }}
}}
}}
}}
The prosimians were once a group considered a suborder of the primate [[Order (biology)|order]] (suborder '''Prosimii''' - Gr. ''pro'', before, + Latin ''simius/simia'', ape), which was named in 1811 by [[Johann Karl Wilhelm Illiger]]. They have been shown, however, to be paraphyletic - that is, their most recent common ancestor was a prosimian but it has some non-prosimian descendants (i.e. monkeys and apes). This relationship is shown by the ranks (prosimians in '''bold''') in the list below of the current primate classification between the order and [[Taxonomic rank|infraorder]] level. The term "prosimian" is considered taxonomically obsolete,<ref>{{Cite journal | last1 = Groves | first1 = C. P. | doi = 10.1007/BF02557740 | title = Systematics of tarsiers and lorises | journal = Primates | volume = 39 | issue = 1 | pages = 13–27 | year = 1998 | s2cid = 10869981 }}<!--page 13--></ref> although it is used to emphasize similarities between strepsirrhines, tarsiers, and the early primates.{{Sfn|Hartwig|2011|p=28}}

* Order [[Primate]]s
** '''Suborder [[Strepsirrhini]]''': non-tarsier prosimians
*** '''Infraorder {{extinct}}[[Adapiformes]]''': extinct "lemur-like" primates
*** '''Infraorder [[Lemuriformes]]''': lemurs, lorises, and bushbabies{{efn|name=Lemuriformes}}
** Suborder [[Haplorrhini]]: tarsiers, monkeys and apes
*** '''Infraorder {{extinct}}[[Omomyiformes]]''': extinct "tarsier-like" primates
*** '''Infraorder [[tarsier|Tarsiiformes]]''': tarsiers
*** Infraorder [[Simiiformes]]: New World monkeys, Old World monkeys, apes, and humans

== See also ==
{{commons|Prosimians}}
* [[Evolution of mammals]]
* [[List of primates]]

==Notes==
{{notes}}

==References==
{{reflist|colwidth=30em}}

===Literature cited===
* <!-- {{Sfn|Cartmill|2010}} -->{{cite book | last1 = Cartmill | first1 = M. | chapter = Chapter 2: Primate Classification and Diversity | pages = 10–30 | editor1-last = Platt | editor1-first = M. | editor2-last = Ghazanfar | editor2-first = A | title = Primate Neuroethology | publisher = Oxford University Press | year = 2010 | isbn = 978-0-19-532659-8 }}
* <!-- {{Sfn|Hartwig|2011}} -->{{cite book | last1 = Hartwig | first1 = W. | editor1-last = Campbell | chapter = Chapter 3: Primate evolution | pages = 19–31 | editor1-first = C. J. | editor2-last = Fuentes | editor2-first = A. | editor3-last = MacKinnon | editor3-first = K. C. | editor4-last = Bearder | editor4-first = S. K. | editor5-last=Stumpf | editor5-first = R. M | title = Primates in Perspective | edition = 2nd | publisher = Oxford University Press | year = 2011 | isbn = 978-0-19-539043-8 }}
* <!-- {{Sfn|Rose|2006}} -->{{cite book | last1 = Rose | first1 = K. D. | title = The Beginning of the Age of Mammals | year = 2006 | publisher = Johns Hopkins University Press | isbn = 978-0-8018-8472-6}}
* <!-- {{Sfn|Szalay|Delson|1980}}-->{{cite book | last1 = Szalay | first1 = F.S. | last2 = Delson | first2 = E. | title = Evolutionary History of the Primates | year = 1980 | publisher = [[Academic Press]] | isbn = 978-0126801507 | oclc = 893740473}}

{{Taxonbar|from=Q841759}}

[[Category:Obsolete primate taxa]]
[[Category:Paraphyletic groups]]
[[Category:Taxa named by Johann Karl Wilhelm Illiger]]