Dictionary Meaning and Definition on 'Mammal'
n : any warm-blooded vertebrate having the skin more or less
covered with hair; young are born alive except for the
small subclass of monotremes and nourished with milk
- Mammal \Mam"mal\, n.; pl. Mammals. [L. mammalis belonging to
the breast, fr. mamma the breast or pap: cf. F. mammal.]
One of the Mammalia.
Age of mammals. See under Age, n., 8.
Wikipedia Meaning and Definition on 'Mammal'
Mammals (formally Mammalia) are a class of air-breathing vertebrate animals characterized by the possession of hair, three middle ear bones, a neocortex, and mammary glands functional in mothers with young. Most mammals also possess sweat glands and specialized teeth, and the largest group of mammals, the placentals, have a placenta which feeds the offspring during gestation. The mammalian brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals range in size from the 30–40 millimeter (1- to 1.5-inch) Bumblebee Bat to the 33-meter (108-foot) Blue Whale.
Depending on classification scheme, there are approximately 5,500 species (5,490, according to the IUCN Red List) of mammals, distributed in about 1,200 genera, 153 families, 29 orders divided into three infraclasses in two subclasses: the monotremes of the sublclass Prototheria, and the marsupials and placentals or the subclass Theria. Except for the five species of monotremes (which lay eggs), all mammal species give birth to live young. Most mammals, including the six largest orders, belong to the placental group. The three largest orders, in descending order, are Rodentia (mice, rats, porcupines, beavers, capybaras, and other gnawing mammals), Chiroptera (bats), and Soricomorpha (shrews, moles and solenodons). The next three largest orders include the Carnivora (dogs, cats, weasels, bears, seals, and their relatives), the Cetartiodactyla (including the even-toed hoofed mammals and the whales), and the Primates, to which the human species belongs.[See more about Mammal at Dictionary 3.0 Encyclopedia]
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