Editing Canidae (section)

=={{visible anchor|Characteristics|Anatomy}}==
{{multiple image|direction=vertical|image1=|caption1=Comparative illustration of the paws of the [[wolf]], [[golden jackal]], and [[dhole]] by A. N. Komarov|
|image2=Black-backed Jackal skeleton.jpg|caption2=Skeleton of a [[black-backed jackal]] (''Lupulella mesomelas'') on display at the [[Museum of Osteology]]
|image3=Wolf cranium labelled.jpg|caption3=Diagram of a wolf skull with key features labelled
|image4=Lupocranio.jpg|caption4=[[Eurasian wolf]] skull}}

Wild canids are native to all continents except Australasia and Antarctica, and also occur as [[feral]] (human-introduced) in New Guinea and Australia. They inhabit a wide range of different habitats, including [[deserts]], [[mountains]], [[forests]], and [[grassland]]s. They vary in size from the fennec fox, which may be as little as {{cvt|24|cm}} in length and weigh {{cvt|0.6|kg}},<ref>{{cite book|author=Marc Tyler Nobleman|title=Foxes|url=https://books.google.com/books?id=bwZx2t3D4ukC|year=2007|publisher=Marshall Cavendish|isbn=978-0-7614-2237-2 |page=35}}</ref> to the gray [[wolf]], which may be up to {{cvt|160|cm}} long, and can weigh up to {{cvt|79|kg}}.<ref name="heptner1998">Heptner, V. G.; Naumov, N. P. (1998), [https://archive.org/details/mammalsofsov211998gept Mammals of the Soviet Union Vol. II Part 1a, Sirenia and Carnivora (Sea cows; Wolves and Bears)], Science Publishers, Inc. US., pp.&nbsp;166–176, {{ISBN|1-886106-81-9}}</ref> Only a few species are [[arboreal locomotion|arboreal]]—the [[gray fox]], the closely related [[island fox]]<ref>{{cite web|url=http://animaldiversity.org/site/accounts/information/Urocyon_littoralis.html |title=ADW: ''Urocyon littoralis'': Information |publisher=Animaldiversity.org |date=28 November 1999 |access-date=12 June 2012}}</ref> and the [[raccoon dog]] habitually climb trees.<ref>Kauhala, K.; Saeki, M. (2004). Raccoon Dog«. Canid Species Accounts. IUCN/SSC Canid Specialist Group. Pridobljeno 15 April 2009.</ref><ref>{{cite journal | title = Old dogs, new tricks: Asia's raccoon dog, a venerable member of the canid family is pushing into new frontiers | author = Ikeda, Hiroshi | journal = Natural History | volume = 95 | issue = #8 |pages=40, 44 | date = August 1986}}</ref><ref>{{Cite web |url=http://www.waza.org/en/zoo/visit-the-zoo/dogs-and-hyenas/nyctereutes-procyonoides. |title=Raccoon dog – ''Nyctereutes procyonoides''. WAZA – World Association of Zoos and Aquariums. |access-date=30 August 2011 |archive-url=https://web.archive.org/web/20150410065554/http://www.waza.org/en/zoo/visit-the-zoo/dogs-and-hyenas/nyctereutes-procyonoides |archive-date=10 April 2015 |url-status=dead }}</ref>

All canids have a similar basic form, as exemplified by the gray wolf, although the relative length of muzzle, limbs, ears, and tail vary considerably between species. With the exceptions of the bush dog, the raccoon dog and some domestic [[dog breeds]], canids have relatively long legs and lithe bodies, adapted for chasing prey. The tails are bushy and the length and quality of the pelage vary with the season. The muzzle portion of the skull is much more elongated than that of the cat family. The [[zygomatic arch]]es are wide, there is a transverse [[lambdoidal]] ridge at the rear of the [[cranium]] and in some species, a [[sagittal crest]] running from front to back. The bony orbits around the eye never form a complete ring and the auditory bullae are smooth and rounded.<ref name=Mivart>{{cite book |title=Dogs, Jackals, Wolves, and Foxes: A Monograph of the Canidae |last=Mivart |first=St. George Jackson |year=1890 |pages=xiv–xxxvi |url=https://archive.org/details/dogsjackalswolv00keulgoog |publisher=London : R.H. Porter : Dulau }}</ref> Females have three to seven pairs of [[mammae]].<ref name="Nowak2005">{{cite book|author=Ronald M. Nowak|title=Walker's Carnivores of the World|url=https://books.google.com/books?id=0q5aHw2mFi8C|year=2005|publisher=JHU Press|isbn=978-0-8018-8032-2}}</ref>

All canids are [[digitigrade]], meaning they walk on their toes. The [[Rhinarium|tip of the nose]] is always naked, as are the cushioned pads on the soles of the feet. These latter consist of a single pad behind the tip of each toe and a more-or-less three-lobed central pad under the roots of the digits. Hairs grow between the pads and in the Arctic fox the sole of the foot is densely covered with hair at some times of the year. With the exception of the four-toed [[African wild dog]] (''Lycaon pictus''), five toes are on the forefeet, but the pollex (thumb) is reduced and does not reach the ground. On the hind feet are four toes, but in some domestic dogs, a fifth vestigial toe, known as a [[dewclaw]], is sometimes present, but has no anatomical connection to the rest of the foot. In some species, slightly curved nails are non-retractile and more-or-less blunt<ref name=Mivart/> while other species have sharper, partially-retractile claws.{{cn|date=February 2023}}

The [[canine penis]] contains a [[baculum]] and a structure called the [[bulbus glandis]] that expands during [[copulation (zoology)|copulation]], forming a [[copulatory tie]] that lasts for up to an hour.<ref name="Ewer1973">{{cite book|author=Ewer, R. F. |title=The Carnivores|url=https://books.google.com/books?id=IETMd3-lSlkC|year=1973|publisher=Cornell University Press|isbn=978-0-8014-8493-3}}</ref> Young canids are born blind, with their eyes opening a few weeks after birth.<ref>{{cite book|author= Macdonald, D.|year= 1984|title= The Encyclopedia of Mammals|publisher= Facts on File|location= New York|page= [https://archive.org/details/encyclopediaofma00mals_0/page/57 57]|isbn= 978-0-87196-871-5|url= https://archive.org/details/encyclopediaofma00mals_0/page/57}}</ref> All living canids (Caninae) have a ligament analogous to the [[nuchal ligament]] of [[ungulates]] used to maintain the posture of the head and neck with little active muscle exertion; this ligament allows them to conserve energy while running long distances following scent trails with their nose to the ground. However, based on skeletal details of the neck, at least some of the Borophaginae (such as ''[[Aelurodon]]'') are believed to have lacked this ligament.{{sfn|Wang|Tedford|2008|pp=97–98}}

===Dentition===

[[Dentition]] relates to the arrangement of teeth in the mouth, with the [[Dentition#Dental formula|dental notation]] for the upper-jaw teeth using the upper-case letters I to denote [[incisors]], C for [[Canine tooth|canines]], P for [[premolars]], and M for [[molars]], and the lower-case letters i, c, p and m to denote the [[Mandible|mandible teeth]]. Teeth are numbered using one side of the mouth and from the front of the mouth to the back. In [[carnivores]], the upper premolar P4 and the lower molar m1 form the [[carnassials]] that are used together in a scissor-like action to shear the muscle and tendon of prey.{{sfn|Wang|Tedford|2008|pp=74}}

Canids use their premolars for cutting and crushing except for the upper fourth premolar P4 (the upper carnassial) that is only used for cutting. They use their molars for grinding except for the lower first molar m1 (the lower carnassial) that has evolved for both cutting and grinding depending on the canid's dietary adaptation. On the lower carnassial, the [[trigonid]] is used for slicing and the [[talonid]] is used for grinding. The ratio between the trigonid and the talonid indicates a carnivore's dietary habits, with a larger trigonid indicating a [[hypercarnivore]] and a larger talonid indicating a more [[Omnivore|omnivorous]] diet.<ref name=sansalone2015/><ref name=cherin2013/> Because of its low variability, the length of the lower carnassial is used to provide an estimate of a carnivore's body size.<ref name=sansalone2015/>

A study of the estimated bite force at the canine teeth of a large sample of living and fossil mammalian predators, when adjusted for their body mass, found that for [[placental mammals]] the bite force at the canines <!-- (in [[Newton (unit)|Newtons]]/kilogram of body weight) --> was greatest in the extinct dire wolf (163), followed among the modern canids by the four hypercarnivores that often prey on animals larger than themselves: the African wild dog (142), the gray wolf (136), the [[dhole]] (112), and the [[dingo]] (108). The bite force at the carnassials showed a similar trend to the canines. A predator's largest prey size is strongly influenced by its biomechanical limits.<ref name=wroe2005/>

Most canids have 42 [[teeth]], with a [[dentition|dental formula]] of: {{DentalFormula|upper=3.1.4.2|lower=3.1.4.3}}. The bush dog has only one upper molar with two below, the dhole has two above and two below. and the [[bat-eared fox]] has three or four upper molars and four lower ones.<ref name=Mivart/> The molar teeth are strong in most species, allowing the animals to crack open bone to reach the [[bone marrow|marrow]]. The deciduous, or baby teeth, formula in canids is {{DentalFormula|upper=3.1.3|lower=3.1.3}}, molars being completely absent.<ref name=Mivart/>