Editing Orangutan (section)

== Characteristics ==

[[File:Pongo tapanuliensis male female.jpg|thumb|left|alt=Head and shoulder shots of an adult male and female orangutan|Adult male (left) and female Tapanuli orangutans]]

Orangutans display significant [[sexual dimorphism]]; females typically stand {{cvt|115|cm}} tall and weigh around {{cvt|37|kg}}, while adult males stand {{cvt|137|cm}} tall and weigh {{cvt|75|kg}}. Compared to humans, they have proportionally long arms, a male orangutan having an [[arm span]] of about {{cvt|2|m}}, and short legs. They are covered in long reddish hair that starts out bright orange and darkens to [[maroon]] or [[chocolate (color)|chocolate]] with age, while the skin is grey-black. Though largely hairless, males' faces can develop some hair, giving them a beard.<ref name=Groves1971>{{cite journal|last1=Groves|first1=Colin P.|title=Pongo pygmaeus|journal=[[Mammalian Species]]|date=1971|issue=4|pages=1–6|doi=10.2307/3503852|jstor=3503852}}</ref><ref name="MacDonald"/><ref name=Payne>{{cite book|author1=Payne, J |author2=Prundente, C |year=2008|title=Orangutans: Behaviour, Ecology and Conservation|publisher=[[New Holland Publishers]]|isbn= 978-0-262-16253-1}}</ref>{{rp|13–15}}

Orangutans have small ears and noses; the ears are unlobed.<ref name=Groves1971/> The mean [[Endocranium|endocranial]] volume is 397&nbsp;cm<sup>3</sup>.<ref name="aiello">{{cite book |last1=Aiello|first1= L. |last2=Dean|first2= C. | year=1990 | title=An Introduction to Human Evolutionary Anatomy | publisher=Academic Press | page=193 | isbn=0-12-045590-0}}</ref> The cranium is elevated relative to the face, which is incurved and [[prognathous]].<ref name=Groves1971/> Compared to chimpanzees and gorillas, the [[brow ridge]] of an orangutan is underdeveloped.<ref>{{cite journal|last1=Hilloowala|first1=R. A.|last2=Trent|first2=R. B.|year=1988|title=Supraorbital ridge and masticatory apparatus I: Primates|journal=Human Evolution|volume=3|issue=5|pages=343–50|doi=10.1007/BF02447216|s2cid=83923845}}</ref> Females and juveniles have relatively circular skulls and thin faces while mature males have a prominent [[sagittal crest]], large cheek pads or flanges,<ref name=Groves1971/> extensive throat pouches and long [[Canine tooth|canines]].<ref name=Groves1971/><ref name=Payne />{{rp|14}} The cheek pads are made mostly of fatty tissue and are supported by the musculature of the face.<ref>{{cite journal|author=Winkler, L. A.|year=1989|title=Morphology and relationships of the orangutan fatty cheek pads|journal=[[American Journal of Primatology]]|volume=17|issue=4|pages=305–19|doi=10.1002/ajp.1350170405|pmid=31964053|s2cid=83661029}}</ref> The throat pouches act as [[Vocal resonation|resonance]] chambers for making long calls.<ref name="Utami 2002"/>
[[File:Orang-Utan Tournai.jpg|thumb|upright|alt= An orangutan skeleton|Skeleton of subadult Bornean orangutan]]

Orangutan hands have four long fingers but a dramatically shorter [[opposable thumb]] for a strong grip on branches as they travel high in the trees. The resting configuration of the fingers is curved, creating a suspensory hook grip. With the thumb out of the way, the fingers (and hands) can grip securely around objects with a small diameter by resting the tops of the fingers against the inside of the palm, thus creating a double-locked grip.<ref name=Rose>{{cite book | author=Rose, M. D.| contribution= Functional Anatomy of the Cheirdia |editor = Schwartz, Jeffrey|editor-link=Jeffrey H. Schwartz |title = Orang-utan Biology | year = 1988 | isbn = 978-0-19-504371-6 | publisher = Oxford University Press | page=301}}</ref> Their feet have four long toes and an opposable big toe, giving them hand-like dexterity. The hip joints also allow for their legs to rotate similarly to their arms and shoulders.<ref name=Payne />{{rp|15}}

Orangutans move through the trees by both vertical climbing and [[Suspensory behavior|suspension]]. Compared to other great apes, they infrequently descend to the ground where they are more cumbersome. Unlike gorillas and chimpanzees, orangutans are not true [[Knuckle-walking|knuckle-walkers]], instead bending their digits and walking on the sides of their hands and feet.<ref>{{cite journal|last1=Oishi, M.|last2= Ogihara, N.|last3= Endo, H.|last4= Ichihara, N.|last5= Asari, M.|year=2009|title=Dimensions of forelimb muscles in orangutans and chimpanzees|journal=Journal of Anatomy|volume=215|issue=4|pages=373–82|doi=10.1111/j.1469-7580.2009.01125.x|pmid= 19619166|pmc=2766055}}</ref><ref name="Schwartz">{{cite book | author = Schwartz, Jeffrey | author-link = Jeffrey H. Schwartz | title = The Red Ape: Orangutans and Human Origins | year = 1987 | pages = [https://archive.org/details/isbn_0813340640_0/page/286 6–7] | isbn = 978-0-8133-4064-7 | publisher = [[Westview Press]] |url = https://archive.org/details/isbn_0813340640_0/page/286 }}</ref>

Compared to their relatives in Borneo, Sumatran orangutans are more slender with paler and longer hair and a longer face.<ref name="MacDonald"/> Tapanuli orangutans resemble Sumatran orangutans more than Bornean orangutans in body build and hair colour.<ref name="curbio"/> They have shaggier hair, smaller skulls, and flatter faces than the other two species.<ref name="Reese_A"/>