Mammal

Mammals
Temporal range: 225–0 mya (Kemp)[1]
or 167–0 mya (Rowe)[2]
Common vampire batTasmanian devilFox squirrelPlatypusHumpback whaleGiant armadilloVirginia opossumHumanTree pangolinColugoStar nosed molePlains zebraEastern grey kangarooNorthern elephant sealAfrican elephantReindeerGiant pandaBlack and rufous elephant shrewMammal Diversity 2011.png
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Scientific classification e
Kingdom:Animalia
Phylum:Chordata
Clade:Amniota
Clade:Synapsida
Clade:Mammaliaformes
Class:Mammalia
Linnaeus, 1758
Living subgroups

Mammals are a group of vertebrate animals which form the class Mammalia. They have fur or hair and a very precise kind of temperature regulation.

With the exception of the monotremes, all mammals bear live young. They also produce milk for the young. Parental care of the young is universal among mammals, and it is essential because live birth limits the number of offspring.

Main characteristics

Reproductive cycle

Most marsupial and eutherian mammals have a reproductive cycle known as the oestrous cycle (U.S: estrous cycle). Females are sexually active only during the oestrous stage, when they are 'on heat' for a few days each month. If an ovum is not fertilized, the endometrium (uterus lining) is resorbed. Oestrus cycles may occur once or twice a year, or many times a year. Each group of mammals has its own frequency.

Humans and primates, are quite different. They have a menstrual cycle. In this case, females are sexually receptive at any time, but only fertile when an ovum is released from an ovary. In this case, the endometrium (if not needed for an fertilised egg) is discarded. The endometrium is shed, and takes with it a certain amount of blood. In this system, eggs are released from the ovaries mostly in the middle of the cycle, away from the menstrual period. This ovulation is 'concealed', meaning, it is not obvious when it occurs. This process, so it is thought, tends to keep the male and female together, which is unusual in mammals with the oestrous cycle.

Skeleton

One diagnostic feature is the lower jaw which, unlike earlier forms, is composed of a single bone, the dentary. This is one feature which can be seen in fossils, or at least those which are complete enough to have the lower jaw. Mammals have three little bones in their inner ear, the ear ossicles. The ear ossicles are bones which were, long ago, part of the lower jaw in early proto-mammals.

There are quite a number of other features, particularly in the skull and limbs, so that it is usually possible identify and describe a mammal from its skeleton alone.

Neocortex and behavior

Another diagnostic feature is the neocortex of the brain, which no other vertebrate has. This is involved in the kind of flexible behavior and learning typical of mammals. Reptiles and birds have much of their behavior controlled by "inherited behavior chains", which roughly translates as "instincts". Almost all animals can do some learning, but mammals do far more than other vertebrates. Their behavior is much more flexible than lizards, for example, and that is made possible by their neocortex.

Other things in the life of mammals seem to be connected with this flexibility and learning. Play is a kind of early learning period in which, according to one theory,[3] mammals develop skills which they will need in life. All mammalian young play, and this is very obvious in the more intelligent mammals (primates, cats).

The emotions of mammals are very noticeable, and rather similar to ours. It is possible, and quite common, for humans to have a friendly relationship with another mammal. It is quite impossible for a human to have any kind of relationship with a snake or a gecko (for example). This is because the reptile simply does not have the same basic emotions as a human.

Other items

There are about 50 characters which are typical of mammals, and some of the most important are discussed above. A few more examples will make it clear that mammals are very different from reptiles and birds:

  • Sweat glands
  • Tooth replacement: two sets, and no continuous replacement. Enamel on the tooth surface. Reptile teeth all alike; mammal teeth follow a pattern (incisors, canines, premolars and molars)
  • Occipital condyles. Two knobs at the base of the skull fit into the topmost neck vertebra; most tetrapods, in contrast, have only one such knob
  • Outlet for food waste separate from urinogenital outlet. Reptiles and birds have a common cloaca at the rear
  • Mammals excrete urea; reptiles and birds excrete uric acid
  • Colour vision is defective or absent in most mammals (primates are an exception)
  • In reptiles and birds the blood vessel which carries oxygenated blood from the left ventricle of the heart lies on the right side of the body; but in mammals it lies on the left side.[4]
  • There are many features of the skeleton that mammals share
    • Their neck almost always has seven vertebrae, no matter how long it is.
    • Their lower jaw is made of just a single bone on each side, the dentary.
    • Their inner ear has three tiny bones, the ossicles: malleus, incus and stapes.

In the language of cladistics, these 50 unique characters are apomorphies which prove that mammals are a clade descended from a common ancestor.[1]

Other Languages
Адыгэбзэ: ШэрыпӀхэр
Afrikaans: Soogdier
Alemannisch: Säugetiere
አማርኛ: ጡት አጥቢ
Ænglisc: Sycedēor
العربية: ثدييات
aragonés: Mammalia
asturianu: Mammalia
Avañe'ẽ: Okambúva
Aymar aru: Ñuñuri
azərbaycanca: Məməlilər
تۆرکجه: ممه‌لیلر
Bân-lâm-gú: Chhī-leng tōng-bu̍t
башҡортса: Һөтимәрҙәр
беларуская: Млекакормячыя
беларуская (тарашкевіца)‎: Сысуны
български: Бозайници
Boarisch: Spoviecha
bosanski: Sisari
brezhoneg: Bronneged
буряад: Хүхэтэн
català: Mamífers
Cebuano: Mamipero
čeština: Savci
chiShona: Dzinoyamwisa
corsu: Mammiferu
Cymraeg: Mamal
dansk: Pattedyr
Deutsch: Säugetiere
dolnoserbski: Cycaki
eesti: Imetajad
Ελληνικά: Θηλαστικό
English: Mammal
español: Mammalia
Esperanto: Mamuloj
estremeñu: Mamíferu
euskara: Ugaztun
Fiji Hindi: Mammal
føroyskt: Súgdjór
français: Mammifère
Gaeilge: Mamach
Gaelg: Sheeintagh
Gàidhlig: Mamal
galego: Mamíferos
ГӀалгӀай: Дакхадийнаташ
Gĩkũyũ: Mammal
客家語/Hak-kâ-ngî: Sṳ̍t-nen thung-vu̍t
한국어: 포유류
հայերեն: Կաթնասուն
हिन्दी: स्तनधारी
hornjoserbsce: Cycaki
hrvatski: Sisavci
Ilokano: Mamalia
Bahasa Indonesia: Binatang menyusui
interlingua: Mammiferos
Interlingue: Mammiferes
ᐃᓄᒃᑎᑐᑦ/inuktitut: ᐱᓱᒃᑎ
íslenska: Spendýr
italiano: Mammalia
עברית: יונקים
Basa Jawa: Mamalia
ಕನ್ನಡ: ಸಸ್ತನಿ
Kapampangan: Mammal
kernowek: Bronnvil
Kiswahili: Mamalia
Kreyòl ayisyen: Mamifè
kurdî: Şîrmêj
Кыргызча: Сүт эмүүчү
Latina: Mammalia
latviešu: Zīdītāji
Lëtzebuergesch: Mamendéieren
lietuvių: Žinduoliai
Ligure: Mammalia
Limburgs: Zoogdiere
Lingua Franca Nova: Mamal
la .lojban.: mabru
lumbaart: Mamifer
magyar: Emlősök
македонски: Цицачи
മലയാളം: സസ്തനി
Malti: Mammiferu
მარგალური: ძუძუშმაწუალეფი
مصرى: ثدييات
Bahasa Melayu: Mamalia
Baso Minangkabau: Binatang manyusuan
Mìng-dĕ̤ng-ngṳ̄: Buô-ṳ̄ dông-ŭk
монгол: Хөхтөн
မြန်မာဘာသာ: နို့တိုက်သတ္တဝါ
Nederlands: Zoogdieren
Nedersaksies: Zoogdeers
日本語: 哺乳類
Napulitano: Mammifere
Nordfriisk: Tetjdiarten
norsk: Pattedyr
norsk nynorsk: Pattedyr
Nouormand: Mammiféthe
Novial: Mammalia
occitan: Mammalia
олык марий: Шӧр пукшышо
Oromoo: Hoosiftoota
oʻzbekcha/ўзбекча: Sut emizuvchilar
ਪੰਜਾਬੀ: ਥਣਧਾਰੀ
Pälzisch: Säugetiere
پنجابی: ددپلانے
Patois: Mamal
Перем Коми: Нимӧтчиссез
ភាសាខ្មែរ: ថនិកសត្វ
Piemontèis: Mamìfer
Plattdüütsch: Söögdeerten
polski: Ssaki
português: Mamíferos
română: Mamifer
rumantsch: Mammals
Runa Simi: Ñuñuq
русиньскый: Ссавцї
саха тыла: Кыыл
Gagana Samoa: Mamele
संस्कृतम्: सस्तनः
Scots: Mammal
Seeltersk: Suugedierte
shqip: Gjitari
sicilianu: Mammalia
سنڌي: مئمل
slovenčina: Cicavce
slovenščina: Sesalci
Soomaaliga: Naasley
کوردی: گوانداران
српски / srpski: Сисари
srpskohrvatski / српскохрватски: Sisavac
Basa Sunda: Mamalia
svenska: Däggdjur
Tagalog: Mamalya
தமிழ்: பாலூட்டி
татарча/tatarça: Имезүчеләр
తెలుగు: క్షీరదాలు
tetun: Mamíferu
тоҷикӣ: Ширхӯрон
ᏣᎳᎩ: ᎺᎹᎵ
Türkçe: Memeliler
удмурт: Пӧйшур
українська: Ссавці
اردو: ممالیہ
vèneto: Mamìfari
Tiếng Việt: Lớp Thú
Võro: Imetäjä
West-Vlams: Zoogbêestn
Winaray: Mammalia
吴语: 哺乳動物
ייִדיש: זויגער
粵語: 哺乳動物
Zazaki: Çıçeyıni
Zeêuws: Zoogdieren
žemaitėška: Žvierē
中文: 哺乳动物