Editing Ungulate (section)

====Cranial appendages====
{{See also|Horn (anatomy)|Ossicone|Antler}}
[[File:Red deer stag velvet.jpg|thumb|upright|[[velvet antler|Velvet]] covers a growing antler and provides it with blood, supplying oxygen and nutrients.]]

Ungulates have evolved a variety of cranial appendages that can be found in [[Pecora|cervoids]] (with the exception of musk deer). In oxen and antelope, the size and shape of the [[horn (anatomy)|horns]] varies greatly but the basic structure is always a pair of simple bony protrusions without branches, often having a spiral, twisted, or fluted form, each covered in a permanent sheath of [[keratin]]. The unique horn structure is the only unambiguous morphological feature of bovids that distinguishes them from other [[pecorans]].<ref>{{cite journal |last1=Bibi |first1=F. |last2=Bukhsianidze |first2=M. |last3=Gentry |first3=A. |last4=Geraads |first4=D. |last5=Kostopoulos |first5=D. |last6=Vrba |first6=E. |year=2009 |title=The fossil record and evolution of Bovidae: State of the field |url=http://palaeo-electronica.org/2009_3/169/index.html |journal=Palaeontologia Electronica |volume=12 |issue=3 |pages=10A}}</ref><ref>{{cite journal|last=Gatesy|first=J.|author2=Yelon, D., DeSalle, R., Vrba, E. |year=1992|title=Phylogeny of the Bovidae (Artiodactyla, Mammalia), Based on Mitochondrial Ribosomal DNA Sequences|journal=Mol. Biol. Evol.|volume=9|issue=3|pages=433–446|pmid=1584013|doi=10.1093/oxfordjournals.molbev.a040734|doi-access=free}}</ref> Male horn development has been linked to sexual selection,<ref name=BroJ>{{cite journal|doi=10.1111/j.1558-5646.2007.00111.x|last=Bro-Jørgensen|first=J.|year=2007|title=The intensity of sexual selection predicts weapon size in male bovids|journal=Evolution|volume=61|issue=6|pages=1316–1326|pmid=17542842|s2cid=24278541|doi-access=free}}</ref><ref>{{cite journal|last=Ezenwa|first=V.|author2=Jolles, A. |year=2008|title=Horns honestly advertise parasite infection in male and female African buffalo|journal=Animal Behaviour|doi=10.1016/j.anbehav.2007.12.013|volume=75|pages=2013–2021|issue=6|s2cid=49240459}}</ref> while the presence of horns in females is likely due to natural selection.<ref name=BroJ/><ref name=Stankowich>{{cite journal|last=Stankowich|first=T.|author2=Caro, T. |author2-link=Tim Caro |year=2009|title=Evolution of weaponry in female bovids|journal=[[Proceedings of the Royal Society B]]|pmid=19759035|doi=10.1098/rspb.2009.1256|volume=276|issue=1677|pages=4329–34|pmc=2817105}}</ref> The horns of females are usually smaller than those of males and are sometimes of a different shape. The horns of female bovids are thought to have evolved for defense against [[predator]]s or to express territoriality, as nonterritorial females, which are able to use [[crypsis]] for predator defense, often lack horns.<ref name=Stankowich/>

Rhinoceros horns, unlike those of other horned mammals, consist only of keratin. These horns rest on the nasal ridge of the animal's skull.

[[Antler]]s are unique to cervids and found mostly on males: the only cervid females with antlers are [[reindeer|caribou and reindeer]], whose antlers are normally smaller than males'. Nevertheless, fertile [[wiktionary:doe#English|does]] of other species of deer have the capacity to produce antlers on occasion, usually due to increased testosterone levels.<ref>[http://www.das.psu.edu/research-extension/deer/photos/antlered-doe Antlered Doe] {{webarchive|url=https://web.archive.org/web/20120229040529/http://www.das.psu.edu/research-extension/deer/photos/antlered-doe |date=2012-02-29 }}</ref> Each antler grows from an attachment point on the skull called a pedicle. While an antler is growing it is covered with highly [[Blood vessel|vascular]] [[skin]] called velvet, which supplies oxygen and nutrients to the growing bone.<ref name=Hall>{{Cite book | last = Hall | first = Brian K. | year = 2005 | title = Bones and Cartilage: Developmental and Evolutionary Skeletal Biology | publisher = Academic Press | chapter = Antlers | pages = 103–114 | isbn = 978-0-12-319060-4 | chapter-url = https://books.google.com/books?id=y-RWPGDONlIC&pg=PA103 | access-date = 2010-11-08 }}</ref>  Antlers are considered one of the most exaggerated cases of male secondary sexual traits in the animal kingdom,<ref name="Malo">{{cite journal | last1 = Malo | first1 = A. F. | last2 = Roldan | first2 = E. R. S. | last3 = Garde | first3 = J. | last4 = Soler | first4 = A. J. | last5 = Gomendio | first5 = M. | year = 2005 | title = Antlers honestly advertise sperm production and quality | journal = Proceedings of the Royal Society B | volume = 272 | issue = 1559| pages = 149–157 | doi=10.1098/rspb.2004.2933 | pmid=15695205 | pmc=1634960}}</ref> and grow faster than any other mammal bone.<ref name=W&H>{{Cite book | last1 = Whitaker | first1 = John O. | last2 = Hamilton | first2 = William J. Jr. | year = 1998 | title = Mammals of the Eastern United States | publisher = Cornell University Press | page = 517 | isbn = 978-0-8014-3475-4 | url = https://books.google.com/books?id=5fVymWAez-YC&pg=PA517 | access-date = 2010-11-08 }}</ref>  Growth occurs at the tip, initially as [[cartilage]] that is then mineralized to become bone. Once the antler has achieved its full size, the velvet is lost and the antler's bone dies. This dead bone structure is the mature antler. In most cases, the bone at the base is destroyed by [[osteoclast]]s and the antlers eventually fall off.<ref name=Hall/> As a result of their fast growth rate antlers place a substantial nutritional demand on deer; they thus can constitute an honest signal of metabolic efficiency and food gathering capability.<ref name="Ditchkoff">{{cite journal | last1 = Ditchkoff | first1 = S. S. | last2 = Lochmiller | first2 = R. L. | last3 = Masters | first3 = R. E. | last4 = Hoofer | first4 = S. R. | last5 = Den Bussche | first5 = R. A. Van | year = 2001 | title = Major-histocompatibility-complex-associated variation in secondary sexual traits of white-tailed deer (Odocoileus virginianus): evidence for good-genes advertisement | journal = Evolution | volume = 55 | issue = 3| pages = 616–625 | doi=10.1111/j.0014-3820.2001.tb00794.x | pmid=11327168| s2cid = 10418779 | doi-access = free }}</ref>

[[Ossicone]]s are horn-like (or antler-like) protuberances found on the heads of giraffes and male [[okapi]]s. They are similar to the horns of [[antelope]]s and [[cattle]] save that they are derived from ossified [[cartilage]],<ref>"The Nashville Zoo at Grassmere - Animals :: Masai Giraffe". The Nashville Zoo at Grassmere, n.d. Web. 15 Feb. 2010. {{cite web|title=The Nashville Zoo at Grassmere - Animals :: Masai Giraffe|url=http://www.nashvillezoo.org/animals_detail.asp?animalID=12|url-status=dead|archive-url=https://web.archive.org/web/20101220142807/http://nashvillezoo.org/animals_detail.asp?animalID=12|archive-date=2010-12-20|access-date=2013-02-10}}</ref> and that the ossicones remain covered in [[skin]] and [[fur]] rather than horn.

[[Pronghorn]] cranial appendages are unique. Each "horn" of the pronghorn is composed of a slender, laterally flattened blade of bone that grows from the frontal bones of the skull, forming a permanent core. As in the Giraffidae, skin covers the bony cores, but in the pronghorn it develops into a keratinous sheath that is shed and regrown on an annual basis. Unlike the horns of the family Bovidae, the horn sheaths of the pronghorn are branched, each sheath possessing a forward-pointing tine (hence the name pronghorn). The horns of males are well developed.