“Mammalia”的概念、定义、翻译、参考文献-科学参考

Mammalia

Biology

A class of vertebrates containing some 5700 species. Mammals are warm-blooded animals (see homoiothermy), typically having sweat glands whose secretion cools the skin and an insulating body covering of hair. All female mammals have mammary glands, which secrete milk to nourish the young. Mammalian teeth are differentiated into incisors, canines, premolars, and molars and the middle ear contains three sound-conducting ear ossicles. The four-chambered heart enables complete separation of oxygenated and deoxygenated blood and a muscular diaphragm takes part in breathing movements, both of which ensure that the tissues are well supplied with oxygen. This, together with well-developed sense organs and brain, have enabled mammals to pursue an active life and to colonize a wide variety of habitats.
Mammals evolved from synapsid ancestors during the Triassic period, and the first true mammals emerged during the Jurassic (201 to 145 mya). There are two subclasses: the primitive egg-laying Prototheria (monotremes) and the Theria, which includes all other mammals and consists of the infraclasses Metatheria (marsupials) and Eutheria (placental mammals).

Geology and Earth Sciences

Class of homoiothermic animals in which the head is supported by a flexible neck, typically with seven vertebrae, articulating through two occipital condyles. The lower jaw is composed of one bone only, the dentary, which articulates directly with the skull; the middle ear contains three small bones, two of which are derived from bones in the lower jaw of reptiles. Typically, mammalian teeth are of differing forms (heterodont), they are set in sockets (thecodont), and milk teeth are shed and replaced by a second set. A hard palate separates the nasal cavity from the mouth. Except in monotremes, the egg is small and develops in the uterus; and the young are fed milk secreted by mammae (which give the class its name). The skin has at least a few hairs. Many mammalian features were present in therapsids (mammal-like reptiles) during the Triassic. Mammals are believed to have appeared first toward the end of the Triassic and to have diversified rapidly from the end of the Mesozoic, 100 Ma later, following the mass extinction which marks the Mesozoic–Tertiary boundary 65 Ma ago.

单词	Mammalia
释义	Mammalia Biology A class of vertebrates containing some 5700 species. Mammals are warm-blooded animals (see homoiothermy), typically having sweat glands whose secretion cools the skin and an insulating body covering of hair. All female mammals have mammary glands, which secrete milk to nourish the young. Mammalian teeth are differentiated into incisors, canines, premolars, and molars and the middle ear contains three sound-conducting ear ossicles. The four-chambered heart enables complete separation of oxygenated and deoxygenated blood and a muscular diaphragm takes part in breathing movements, both of which ensure that the tissues are well supplied with oxygen. This, together with well-developed sense organs and brain, have enabled mammals to pursue an active life and to colonize a wide variety of habitats. Mammals evolved from synapsid ancestors during the Triassic period, and the first true mammals emerged during the Jurassic (201 to 145 mya). There are two subclasses: the primitive egg-laying Prototheria (monotremes) and the Theria, which includes all other mammals and consists of the infraclasses Metatheria (marsupials) and Eutheria (placental mammals). Geology and Earth Sciences Class of homoiothermic animals in which the head is supported by a flexible neck, typically with seven vertebrae, articulating through two occipital condyles. The lower jaw is composed of one bone only, the dentary, which articulates directly with the skull; the middle ear contains three small bones, two of which are derived from bones in the lower jaw of reptiles. Typically, mammalian teeth are of differing forms (heterodont), they are set in sockets (thecodont), and milk teeth are shed and replaced by a second set. A hard palate separates the nasal cavity from the mouth. Except in monotremes, the egg is small and develops in the uterus; and the young are fed milk secreted by mammae (which give the class its name). The skin has at least a few hairs. Many mammalian features were present in therapsids (mammal-like reptiles) during the Triassic. Mammals are believed to have appeared first toward the end of the Triassic and to have diversified rapidly from the end of the Mesozoic, 100 Ma later, following the mass extinction which marks the Mesozoic–Tertiary boundary 65 Ma ago.
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