Even-toed ungulate 46764 224619527 2008-07-09T18:07:08Z Grebaldar 7387784 {{Refimprove|date=February 2007}} {{Taxobox | name = Even-toed ungulates | fossil_range = Early [[Eocene]] - Recent | image = Masai Giraffe right-rear foot.jpg | image_caption = Right-rear foot of a [[Masai Giraffe]] (''Giraffa camelopardalis tippelskirchi'') at the [[San Diego Zoo]] | regnum = [[Animal]]ia | phylum = [[Chordate|Chordata]] | classis = [[Mammalia]] | infraclassis = [[Eutheria]] | superordo = [[Laurasiatheria]] | ordo = '''Artiodactyla'''[[paraphyly|*]] | ordo_authority = [[Richard Owen|Owen]], 1848 | subdivision_ranks = Families | subdivision = [[Antilocapridae]]<br> [[Bovidae]]<br> [[Camelidae]]<br> [[Cervidae]]<br> [[Giraffidae]]<br> [[Hippopotamidae]]<br> [[Moschidae]]<br> [[Suidae]]<br> [[Tayassuidae]]<br> [[Tragulidae]]<br> [[Leptochoeridae]] [[extinction|†]]<br> [[Dichobunidae]] †<br> [[Cebochoeridae]] †<br> [[Entelodontidae]] †<br> [[Anoplotheriidae]] †<br> [[Anthracotheriidae]] †<br> [[Cainotheriidae]] †<br> [[Agriochoeridae]] †<br> [[Merycoidodontidae]] †<br> [[Leptomerycidae]] †<br> [[Protoceratidae]] †<br> [[Oromerycidae]] †<br> [[Xiphodontidae]] †<br> [[Amphimerycidae]] †<br> [[Helohyidae]] †<br> [[Gelocidae]] †<br> [[Dromomerycidae]] †<br> [[Raoellidae]] †<br> [[Choeropotamidae]] †<br> [[Sanitheriidae]] †<br> [[Climacoceratidae]] †<br> [[Palaeomerycidae]] †<br> }} The '''even-toed ungulates''' form the [[mammal]] [[order (biology)|order]] '''Artiodactyla'''. They are [[ungulate]]s whose weight is borne (if they have more than two toes) about equally by the third and fourth toes, rather than mostly or entirely by the third as in [[perissodactyls]]. Another key distinguishing feature is the shape of the [[Talus bone|astragalus]] (a bone in the [[Hock (zoology)|hock]] joint), which has a double-pulley structure in artiodactyls, giving the foot greater flexibility.<ref name=MamEv>{{cite book |author= Savage, RJG, & Long, MR|year=1986 |title= Mammal Evolution: an illustrated guide|publisher= Facts on File|location=New York|pages= 208|isbn= 0-8160-1194-X}}</ref> There are about 220 artiodactyl [[species]], including many that are of great nutritional, [[economic]] and cultural importance to humans. == Evolution == As with many animal groups, even-toed ungulates first appeared during the Early [[Eocene]] (about 54 million years ago). In form they were rather like today's [[chevrotain]]s: small, short-legged creatures that ate [[leaves]] and the soft parts of [[plants]]. By the Late Eocene (46 million years ago), the three modern suborders had already developed: [[Suina]] (the [[pig]] group); [[Tylopoda]] (the [[camel]] group); and [[Ruminantia]] (the [[goat]] and [[cattle]] group). Nevertheless, artiodactyls were far from dominant at that time: the [[odd-toed ungulate]]s (ancestors of today's [[horse]]s and [[Rhinoceros|rhino]]s) were much more successful and far more numerous. Even-toed ungulates survived in niche roles, usually occupying marginal [[habitat (ecology)|habitats]], and it is presumably at that time that they developed their complex [[digestive system]]s, which allowed them to survive on lower-grade food. The appearance of [[Poaceae|grasses]] during the [[Eocene]] and their subsequent spread during the [[Miocene]] (about 20 million years ago) saw a major change: grasses are very difficult to eat and the even-toed ungulates with their highly-developed [[stomach]]s were better able to adapt to this coarse, low-[[nutrition]] diet, and soon replaced the odd-toed ungulates as the dominant [[Landform|terrestrial]] [[herbivore]]s. Now-extinct Artiodactyla which developed during the [[Miocene]] include the species [[Ampelomeryx]], [[Tauromeryx]], [[Triceromeryx]], and others. === Suina === Suina ([[pigs]] and [[peccary|peccaries]]) are artiodactyls that retain four toes of fairly equal size, have simpler [[molar (tooth)|molars]], short legs, and often have enlarged [[canine teeth]] that form [[tusk]]s. In general, they are [[omnivore]]s and have a simple stomach, except for the two [[hippopotamus]] species and the [[babirusa]] which are herbivores.<ref name=EoM>{{cite book |editor=Macdonald, D.|author= Janis, Christine & Jarman, Peter|year=1984 |title= The Encyclopedia of Mammals|publisher= Facts on File|location=New York|pages= 498-499|isbn= 0-87196-871-1}}</ref> [[Hippopotamidae]] have been considered a member of [[Suina]], however, recent morphological and genetic research suggests that hippos are more closely related to [[whales]].<ref name="DNA">{{Cite journal | url = http://mbe.oxfordjournals.org/cgi/content/abstract/14/5/537 | title = More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen | author = Gatesy, J. | journal = [[Molecular Biology and Evolution]] | volume = 14 | pages = 537–543 | pmid = 9159931}}</ref> === Camelids and Ruminantia === [[Camelid]]s and [[Ruminantia]] tend to be longer-legged, to walk on only the central two toes (though the outer two may survive as rarely-used dew-claws) and to have more complex cheek teeth well-suited to grinding up tough grasses. They have evolved a highly developed digestive process in which partly-digested food is [[regurgitation|regurgitated]] and re-chewed (''chewing the [[cud]]'' or ''cudding''). This complex digestion takes place in a multi-chambered stomach, the [[rumen]] itself. It allows them to use [[fermentation]] by [[microorganisms]] to digest [[cellulose]], a plant material which animals cannot digest directly.<ref name=EoM/> === Cetaceans === One group of artiodactyls (which [[molecular biology]] suggests were most closely related to Hippopotamidae) returned to the sea [[Evolution of cetaceans|to become whales]]. Thus Artiodactyla without [[Cetacea]] is a [[Paraphyly|paraphyletic group]]. For this reason, the term '''[[Cetartiodactyla]]''' was coined to refer to the group containing both artiodactyls and whales.<ref name="Cetartiodactyla">{{cite journal |last=Boisserie |first=Jean-Renaud |coauthors= Fabrice Lihoreau and Michel Brunet |year= 2005 |month= February |title= The position of Hippopotamidae within Cetartiodactyla |journal= [[Proceedings of the National Academy of Sciences]] |volume= 102 |issue= 5 |pages= 1537–1541|url= http://www.pnas.org/cgi/content/full/102/5/1537|accessdate= 2007-06-09 |doi= 10.1073/pnas.0409518102 |pmid= 15677331}}</ref> == Classification == * '''[[Cetartiodactyla]]''' (unranked [[clade]], higher than Artiodactyla) ** Family [[Hippopotamidae]]: hippos ** '''Order''' [[Cetaceans]]: whales, dolphins and porpoises ** '''ORDER ARTIODACTYLA''' *** '''Suborder [[Suina]]''' **** Family [[Suidae]]: pigs **** Family [[Tayassuidae]]: peccaries *** '''Suborder [[Tylopoda]]''' **** Family [[Camelidae]]: camels and [[llama]]s *** '''Suborder [[Ruminantia]]''' **** '''Infraorder [[Pecora]]''' ***** Family [[Antilocapridae]]: [[pronghorn]] ***** Family [[Bovidae]]: cattle, goats, [[sheep]], and [[antelope]] ***** Family [[Cervidae]]: [[deer]] ***** Family [[Giraffidae]]: [[Giraffe]] and [[Okapi]] ***** Family [[Moschidae]]: musk deer **** '''Infraorder [[Tragulina]]''' ***** Family [[Tragulidae]]: chevrotains == See also == * [[Odd-toed ungulate]] ==References== {{commonscat|Artiodactyla}} {{Wikispecies|Artiodactyla}} {{reflist}} {{Mammals}} {{Artiodactyla}} [[Category:Even-toed ungulates| ]] [[ar:شفعيات الأصابع]] [[ang:Cliferfētedēor]] [[an:Artiodactyla]] [[ast:Artiodactyla]] [[zh-min-nan:Ngó͘-tê tōng-bu̍t]] [[bs:Papkari]] [[bg:Чифтокопитни]] [[ca:Artiodàctil]] [[cs:Sudokopytníci]] [[da:Parrettåede hovdyr]] [[de:Paarhufer]] [[el:Αρτιοδάκτυλα]] [[es:Artiodactyla]] [[eo:Parhufuloj]] [[eu:Artiodaktilo]] [[fa:جفت‌سمان]] [[fr:Artiodactyla]] [[gl:Artiodáctilo]] [[ko:소목]] [[hr:Parnoprstaši]] [[io:Para-hufajo]] [[id:Hewan berkuku genap]] [[ia:Artiodactyla]] [[is:Klaufdýr]] [[it:Artiodactyla]] [[he:מכפילי פרסה]] [[jv:Kéwan kuku genep]] [[la:Artiodactyla]] [[lb:Artiodactyla]] [[lt:Porakanopiai]] [[li:Evehovege]] [[hu:Párosujjú patások]] [[nl:Evenhoevigen]] [[ja:ウシ目]] [[no:Partåede hov- og klovdyr]] [[nn:Klauvdyr]] [[oc:Artiodactyla]] [[pl:Parzystokopytne]] [[pt:Artiodátilos]] [[ro:Artiodactyla]] [[qu:Iskay ruk'anayuq]] [[ru:Парнокопытные]] [[simple:Even-toed ungulate]] [[sk:Párnokopytníky]] [[sl:Sodoprsti kopitarji]] [[fi:Sorkkaeläimet]] [[sv:Partåiga hovdjur]] [[vi:Bộ Guốc chẵn]] [[tr:Çift toynaklılar]] [[uk:Парнокопитні]] [[zea:Evenoevihen]] [[zh:偶蹄目]]