Editing Bone (section)

==Other animals==
{{Main|Bird anatomy|Exoskeleton}}
[[File:Fluworôze egzostozes1-800h.jpg|thumb|right|180px|alt=knobby hoofed leg|[[Skeletal fluorosis]] in a cow's leg, due to industrial contamination]]
[[File:Bird leg and pelvic girdle skeleton EN.gif|thumb|left|200px|Leg and pelvic girdle bones of bird]]
[[Bird]] skeletons are very lightweight. Their bones are smaller and thinner, to aid flight. Among mammals, [[bat]]s come closest to birds in terms of bone density, suggesting that small dense bones are a flight adaptation. Many bird bones have little marrow due to them being hollow.<ref name="RSPB-BirdBoneDensity">{{cite journal | vauthors = Dumont ER | title = Bone density and the lightweight skeletons of birds | journal = Proceedings. Biological Sciences | volume = 277 | issue = 1691 | pages = 2193–2198 | date = July 2010 | pmid = 20236981 | pmc = 2880151 | doi = 10.1098/rspb.2010.0117 }}</ref>

A bird's [[beak]] is primarily made of bone as projections of the [[mandible]]s which are covered in [[keratin]].

Some bones, primarily formed separately in subcutaneous tissues, include headgears (such as bony core of horns, antlers, ossicones), osteoderm, and [[os penis]]/[[os clitoris]].<ref>{{cite journal | vauthors = Nasoori A | title = Formation, structure, and function of extra-skeletal bones in mammals | journal = Biological Reviews of the Cambridge Philosophical Society | volume = 95 | issue = 4 | pages = 986–1019 | date = August 2020 | pmid = 32338826 | doi = 10.1111/brv.12597 | s2cid = 216556342 }}</ref> A [[deer]]'s [[antler]]s are composed of bone which is an unusual example of bone being outside the skin of the animal once the velvet is shed.<ref name="pmid10321994">{{cite journal | vauthors = Rolf HJ, Enderle A | title = Hard fallow deer antler: a living bone till antler casting? | journal = The Anatomical Record | volume = 255 | issue = 1 | pages = 69–77 | date = May 1999 | pmid = 10321994 | doi = 10.1002/(SICI)1097-0185(19990501)255:1<69::AID-AR8>3.0.CO;2-R | doi-access = free }}</ref>

The extinct predatory fish ''[[Dunkleosteus]]'' had sharp edges of hard exposed bone along its jaws.<ref>{{Cite web|url=https://www.amnh.org/exhibitions/permanent-exhibitions/fossil-halls/hall-of-vertebrate-origins/dunkleosteus|title=Dunkleosteus|website=American Museum of Natural History}}</ref><ref>{{Cite web|url=https://www.cmnh.org/dunkjaws|title=My, What a Big Mouth You Have {{pipe}} Cleveland Museum of Natural History}}</ref>

The proportion of cortical bone that is 80% in the human skeleton may be much lower in other animals, especially in [[marine mammal]]s and [[marine turtles]], or in various [[Mesozoic]] [[marine reptile]]s, such as [[ichthyosaur]]s,<ref name="Buff&Maz90">{{cite journal | vauthors = de Buffrénil V, Mazin JM | year = 1990 | title = Bone histology of the ichthyosaurs: comparative data and functional interpretation | jstor = 2400968 | journal = Paleobiology | volume = 16 | issue = 4| pages = 435–447 |doi=10.1017/S0094837300010174 |bibcode=1990Pbio...16..435D |s2cid=88171648 }}</ref> among others.<ref name=ZL11>{{cite journal| vauthors = Laurin M, Canoville A, Germain D | year=2011 |title=Bone microanatomy and lifestyle: a descriptive approach |journal=Comptes Rendus Palevol |volume=10 |issue=5–6 |pages=381–402 | doi = 10.1016/j.crpv.2011.02.003}}</ref> This proportion can vary quickly in evolution; it often increases in early stages of returns to an aquatic lifestyle, as seen in early [[whale]]s and [[pinniped]]s, among others. It subsequently decreases in pelagic taxa, which typically acquire spongy bone, but aquatic taxa that live in shallow water can retain very thick, [[Pachyostosis|pachyostotic]],<ref>{{cite journal | vauthors = Houssaye A, De Buffrenil V, Rage JC, Bardet N |title=An analysis of vertebral 'pachyostosis' in Carentonosaurus mineaui (Mosasauroidea, Squamata) from the Cenomanian (early Late Cretaceous) of France, with comments on its phylogenetic and functional significance |journal=Journal of Vertebrate Paleontology |date=12 September 2008 |volume=28 |issue=3 |pages=685–691 |doi=10.1671/0272-4634(2008)28[685:AAOVPI]2.0.CO;2 |s2cid=129670238  |issn=0272-4634}}</ref> [[Osteosclerosis|osteosclerotic]], or pachyosteosclerotic<ref>{{cite journal | vauthors = de Buffrénil V, Canoville A, D'Anastasio R, Domning DP  |title=Evolution of Sirenian Pachyosteosclerosis, a Model-case for the Study of Bone Structure in Aquatic Tetrapods |journal=Journal of Mammalian Evolution |date=June 2010 |volume=17 |issue=2 |pages=101–120 |doi=10.1007/s10914-010-9130-1|s2cid=39169019 }}</ref> bones, especially if they move slowly, like [[Sirenia|sea cows]]. In some cases, even marine taxa that had acquired spongy bone can revert to thicker, compact bones if they become adapted to live in shallow water, or in [[Hypersaline lake|hypersaline]] (denser) water.<ref>{{cite journal | vauthors = Dewaele L, Lambert O, Laurin M, De Kock T, Louwye S, de Buffrénil V |title=Generalized Osteosclerotic Condition in the Skeleton of Nanophoca vitulinoides, a Dwarf Seal from the Miocene of Belgium |journal=Journal of Mammalian Evolution |date=December 2019 |volume=26 |issue=4 |pages=517–543 |doi=10.1007/s10914-018-9438-9|s2cid=20885865 |url=https://hal.sorbonne-universite.fr/hal-02550689/file/Dewaele%20et%20al.%20-%202019%20-%20Generalized%20Osteosclerotic%20Condition%20in%20the%20Skelet.pdf }}</ref><ref>{{cite journal | vauthors = Dewaele L, Gol'din P, Marx FG, Lambert O, Laurin M, Obadă T, de Buffrénil V | title = Hypersalinity drives convergent bone mass increases in Miocene marine mammals from the Paratethys | language = English | journal = Current Biology | volume = 32 | issue = 1 | pages = 248–255.e2 | date = January 2022 | pmid = 34813730 | doi = 10.1016/j.cub.2021.10.065 | s2cid = 244485732 | doi-access = free | bibcode = 2022CBio...32E.248D }}</ref><ref>{{cite journal | vauthors = Houssaye A | title = Evolution: Back to heavy bones in salty seas | journal = Current Biology | volume = 32 | issue = 1 | pages = R42–R44 | date = January 2022 | pmid = 35015995 | doi = 10.1016/j.cub.2021.11.049 | bibcode = 2022CBio...32..R42H | url = https://hal.archives-ouvertes.fr/hal-03820094/file/Houssaye_et_al_Current_Biology.pdf | url-status = live | s2cid = 245879886 | archive-url = https://web.archive.org/web/20221123162936/https://hal.archives-ouvertes.fr/hal-03820094/file/Houssaye_et_al_Current_Biology.pdf | archive-date = 2022-11-23 }}</ref>

Many animals, particularly [[herbivore]]s, practice [[osteophagy]]—the eating of bones. This is presumably carried out in order to replenish lacking [[phosphate]].

Many bone diseases that affect humans also affect other vertebrates—an example of one disorder is skeletal fluorosis.
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