artiodactyl

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Artiodactyla

　

WordNet

1. of or relating to or belonging to mammals of the order Artiodactyla (同)artiodactylous, even-toed
2. an order of hooved mammals of the subclass Eutheria (including pigs and peccaries and hippopotami and members of the suborder Ruminantia) having an even number of functional toes (同)order Artiodactyla

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/12/15 20:57:40」(JST)

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Even-toed ungulates Temporal range: 54–0 Ma PreЄ Є O S D C P T J K Pg N Early Eocene - Recent
Bones of right fore feet of existing Artiodactyla. From left to right: Pig (Sus scrofa), Red deer (Cervus elaphus), and Camel (Camelus bactrianus). U = ulna, R = radius, c = cuneiform, l = lunar, s = Scaphoid, u = Unciform, m = Magnum, td = Trapezoid. In the Sheep and the Camel, the long compound bone, supporting the two main (or only) toes is the cannon bone.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Eutheria
Superorder:	Laurasiatheria
Order:	Artiodactyla Owen, 1848
Suborders
Tylopoda Suina Cetruminantia

The even-toed ungulates (Artiodactyla) are ungulates (hoofed animals) whose weight is borne about equally by the third and fourth toes, rather than mostly or entirely by the third as in odd-toed ungulates (perissodactyls), such as horses.

Artiodactyla comes from (Greek: ἄρτιος (ártios), "even", and δάκτυλος (dáktylos), "finger/toe"), so the name "even-toed" is a translation of the description. This group includes pigs, peccaries, hippopotamuses, camels, chevrotains (mouse deer), deer, giraffes, pronghorn, antelopes, sheep, goats, and cattle. The group excludes whales even though DNA sequence data indicate that they share a common ancestor, making the group paraphyletic. The phylogenetically accurate group is Cetartiodactyla.

There are about 220 artiodactyl species, including many that are of great nutritional, economic, and cultural importance to humans.

A further distinguishing feature of the group is the shape of the astragalus (talus), a bone in the ankle joint, which has a double-pulley structure. This gives the foot greater flexibility.

Evolutionary history

As with many mammal groups, even-toed ungulates first appeared during the Early Eocene (about 54 million years ago). In form, they were rather like today's chevrotains: 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 ungulates (ancestors of today's horses and rhinos) were much more successful and far more numerous. Even-toed ungulates survived in niche roles, usually occupying marginal habitats, and it is presumably at that time that they developed their complex digestive systems, which allowed them to survive on lower-grade food.

The appearance of 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 stomachs, were better able to adapt to this coarse, low-nutrition diet, and soon replaced the odd-toed ungulates as the dominant terrestrial herbivores. Now-extinct Artiodactyla that developed during the Miocene include the genera Ampelomeryx, Tauromeryx, Triceromeryx.

Classification

The following classification is based on Spaulding et al., 2009 and the extant families recognised by Mammal Species of the World published in 2005. Currently, the cetaceans and even-toed ungulates have been placed in Cetartiodactyla as sister groups, although DNA analysis has shown cetaceans evolved from within Artiodactyla. The most recent theory into the origins of hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago. This hypothesized ancestral group likely split into two branches around 54 million years ago. One branch would evolve into cetaceans, possibly beginning with the proto-whale Pakicetus from 52 million years ago with other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.

• Order Artiodactyla/Cetartiodactyla
  • Suborder Tylopoda
    • Family †Anoplotheriidae?
    • Family †Choeropotamidae?
    • Family †Cainotheriidae
    • Family †Merycoidodontidae
    • Family †Agriochoeridae
    • Family Camelidae: camels and llamas (6 species)
    • Family †Oromerycidae
    • Family †Xiphodontidae
  • Suborder Suina
    • Family Suidae: pigs (19 species)
    • Family Tayassuidae: peccaries (4 species)
    • Family †Sanitheriidae
  • Suborder Cetruminantia
    • unranked Cetancodontamorpha
      • Genus †Andrewsarchus?
      • Family †Entelodontidae
      • Infraorder Cetancodonta
        • Clade Cetacea: whales (about 90 species)
        • Family †Raoellidae
        • Family †Dichobunidae
        • Family †Helohyidae
        • Family †Cebochoeridae
        • Family †Anthracotheriidae
        • Family Hippopotamidae: hippos (2 species)
    • unranked Ruminantiamorpha
      • Infraorder Tragulina
        • Family †Amphimerycidae
        • Family †Prodremotheriidae
        • Family †Protoceratidae
        • Family †Hypertragulidae
        • Family †Praetragulidae
        • Family Tragulidae: chevrotains (6 species)
        • Family †Archaeomerycidae
        • Family †Lophiomerycidae
      • Infraorder Pecora
        • Family Antilocapridae: pronghorn (1 species)
        • Family Giraffidae: Giraffe and Okapi (2 species)
        • Family †Climacoceratidae
        • Family Moschidae: musk deer (7 species)
        • Family †Leptomerycidae
        • Family Cervidae: deer (49 species)
        • Family †Gelocidae
        • Family †Palaeomerycidae
        • Family †Hoplitomerycidae
        • Family Bovidae: cattle, goats, sheep, and antelope (135 species)

Anatomy, physiology and morphology

Giraffes necking (Giraffa camelopardalis) in Ithala Game Reserve, Northern KwaZulu Natal, South Africa.

The even-toed ungulates stand on an even number of toes; the group's four suborders differ in other characteristics. Suina (pigs and peccaries) have retained four toes of fairly equal size, have simpler molars, short legs, and often have enlarged canine teeth that form tusks. Camelids and Ruminantia tend to be longer-legged, to walk on only the two central 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.

Behaviour

Development through life stages

Diet and feeding

Further information: Ruminant

The ancestors of the even-toed ungulates were omnivores that preferred plant material; now, even-toed ungulates are generally herbivorous, although species in the suborder Suina (pigs and peccaries) are, like their primitive ancestors, omnivores. Larger stomachs and longer intestines have evolved because plant material is more difficult to digest than meat.

Tylopoda (camels, llamas and alpacas) and chevrotains have a three-chambered stomach, while the rest of Ruminantia have four-chambered stomachs. The handicap of a heavy digestive system has increased selective pressure for limb bone adaptations to escape predators. Most species within Suina have a simple two-chambered stomach that allows an omnivorous diet, the babirusa, however, is a herbivore. They have extra maxillary teeth to allow proper mastication of plant material. Most of the fermentation occurs in the caecum with the help of cellulolytic microorganisms. Peccaries, however, have a complex stomach that contains four compartments. Microbial fermentation with the formation of high volatile fatty acid levels has been observed in the fore stomach; it has been proposed that their complex fore stomach is a means to slow digestive passage and increase digestive efficiency. Hippopotamuses have a three-chambered stomach and do not ruminate, they consume grass during the night and may cover large distances (up to 20 miles) to feed. They eat around 68 kg of food each night, also relying on microbes to break down plant material with cellulase.

Rumination occurs in the ruminants (Ruminantia and Tylopoda), whereby food is regurgitated and rechewed then broken down by microbes in the stomach. After ingestion of plant material, it is mixed with saliva in the rumen and reticulum and separates into layers of solid and liquid material. The solids lump together to form a bolus (also known as the cud), this is regurgitated by reticular contractions while the glottis is closed. When the bolus enters the mouth, the fluid is squeezed out with the tongue and reswallowed. The bolus is chewed slowly to completely mix it with saliva and to break down the particle size. Ingested food passes to the 'fermentation chamber' (rumen and reticulum) where it is kept in continual motion by rhythmic contractions of this organ. Cellulytic microbes (bacteria, protozoa, and fungi) produce cellulase, which is needed to break down the cellulose found in plant material. Without this mutual symbiosis, ruminants would find plant material indigestible.

Habitat and distribution

See also: List of even-toed ungulates by population

Even-toed ungulates are found on every continent but Antarctica; they were introduced to Australia and New Zealand by humans.

Relationship with humans

The even-toed ungulates are of more economic and cultural benefit than any other group of mammals. There is clear evidence of antelope being used for food 2 million years ago in the Olduvai Gorge, part of the Great Rift Valley. Cro-Magnons relied heavily on reindeer for food, skins, tools and weapons; with dropping temperatures and increased reindeer numbers at the end of the Pleistocene, they became the prey of choice. By around 12,500 years ago, reindeer remains accounted for 94 percent of bones and teeth found in a cave above the Céou River.

Today, cattle are the basis of a multi-billion dollar industry worldwide. The international trade in beef for 2000 was over $30 billion and represented only 23 percent of world beef production.

Jewish biblical laws of Kashrut define a cloven hoof as one of two key requirements for an animal to be capable of consideration for Kosher consumption.

Conservation

See also

• Odd-toed ungulate

References

English Journal

• Physical and computational fluid dynamics models for the hemodynamics of the artiodactyl carotid rete.

• O'Brien HD1, Bourke J2.
• Journal of theoretical biology.J Theor Biol.2015 Dec 7;386:122-31. doi: 10.1016/j.jtbi.2015.09.008. Epub 2015 Sep 25.
• In the mammalian order Artiodactyla, the majority of arterial blood entering the intracranial cavity is supplied by a large arterial meshwork called the carotid rete. This vascular structure functionally replaces the internal carotid artery. Extensive experimentation has demonstrated that the artiod
• PMID 26403501

• Methane production by two non-ruminant foregut-fermenting herbivores: The collared peccary (Pecari tajacu) and the pygmy hippopotamus (Hexaprotodon liberiensis).

• Vendl C1, Frei S1, Dittmann MT2, Furrer S3, Ortmann S4, Lawrenz A5, Lange B6, Munn A7, Kreuzer M8, Clauss M9.
• Comparative biochemistry and physiology. Part A, Molecular & integrative physiology.Comp Biochem Physiol A Mol Integr Physiol.2015 Oct 8. pii: S1095-6433(15)00252-4. doi: 10.1016/j.cbpa.2015.09.021. [Epub ahead of print]
• Methane (CH4) production varies between herbivore species, but reasons for this variation remain to be elucidated. Here, we report open-circuit chamber respiration measurements of CH4 production in four specimens each of two non-ruminant mammalian herbivores with a complex forestomach but largely di
• PMID 26454225

• Molecular characterization of T-cell immunoglobulin mucin domain-3 and Galectin-9 genes of swamp- and riverine-type water buffaloes.

• Duran PL1, Padiernos RB2, Abella EA1, Konnai S3, Mingala CN2,4.
• International journal of immunogenetics.Int J Immunogenet.2015 Oct 6. doi: 10.1111/iji.12235. [Epub ahead of print]
• Molecular characterization of T-cell immunoglobulin mucin domain-3 (TIM-3) and Galectin-9 (GAL-9) genes of swamp- and riverine-type water buffaloes was conducted to compare these genes with other species; determine the unique characteristic specific in water buffalo; and provide baseline information
• PMID 26441033

Japanese Journal

• ミャンマー中部の新第三系イラワジ動物相:奇蹄目・偶蹄目

• 西岡 佑一郎,鍔本 武久,タウン ・ タイ,ジン ・ マウン ・ マウン ・ テイン,高井 正成
• 化石 104(0), 5-20, 2018
• … The upper Neogene Pegu Group and Irrawaddy beds of Central Myanmar yield abundant perissodactyl and artiodactyl (cetartiodactyl) fossils. … The late Pliocene fauna is basically not different from the latest Miocene/ early Pliocene fauna because many perissodactyl and artiodactyl species continuously occur from both horizons of the Irrawaddy beds. …
• NAID 130007623343

• Histological Properties of Main and Accessory Olfactory Bulbs in the Common Hippopotamus

• Kondoh Daisuke,Watanabe Kenichi,Nishihara Kaori,Ono Yurie,Nakamura Kentaro,Yuhara Kazutoshi,Tomikawa Sohei,Sugimoto Miki,Kobayashi Saori,Horiuchi Noriyuki,Kobayashi Yoshiyasu,Sasaki Motoki,Kitamura Nobuo
• Brain, behavior and evolution 90(3), 224-231, 2017-11
• … These findings suggest that the olfactory system of the hippopotamus is as well developed as that of other artiodactyl species and that the hippopotamus might depend on its olfactory system for terrestrial social communication. …
• NAID 120006540779

• 幕別町忠類から産出した偶蹄類臼歯化石の再検討

• 髙桒 祐司,添田 雄二
• 北海道開拓記念館研究紀要 (43), 21-26, 2015
• NAID 40020511282

Related Links

• artiodactyl | mammal | Britannica.com

Artiodactyl, any member of the mammalian order Artiodactyla, or even-toed ungulates, which includes the pigs, peccaries, hippopotamuses, camels, chevrotains, deer, giraffes, pronghorn, antelopes, sheep, goats, and cattle. It is one ...

• Artiodactyl | Define Artiodactyl at Dictionary.com

a hoofed, even-toed mammal of the order Artiodactyla, comprising the pigs, hippopotamuses, camels, deer, giraffes, pronghorns, sheep, goats, antelope, and cattle. ... The artiodactyl group must have quickly branched in turn, as we ...

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リンク元	「偶蹄類」「Artiodactyla」

「偶蹄類」

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英

artiodactyl、Artiodactyla

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偶蹄目

「Artiodactyla」

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偶蹄類、偶蹄目

関

artiodactyl