Mammalian

Mammalian is a term that refers to any member of the class Mammalia, a group of warm-blooded vertebrates characterized by the possession of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones. This class contains about 5,400 species grouped into 1,200 genera, which are subdivided into 153 families.

Characteristics

Mammals are distinguished by several unique features. The most distinctive of these is the presence of mammary glands in females which produce milk for the nourishment of young. Other significant characteristics include a neocortex, fur or hair, and three middle ear bones.

Classification

Mammals represent the only living Synapsida, which together with the Sauropsida form the Amniota clade. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. The classification of mammals has been through several iterations since Carl Linnaeus initially defined the class.

Evolution

The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the late Carboniferous period. The most ancestral forms in the class Mammalia are the egg-laying mammals in the subclass Prototheria.

See also

• Mammalogy
• List of mammalian gestation durations
• Mammal classification
• Mammal tooth

External links

• American Society of Mammalogists
• The Mammal Society (UK)

Mammalian Resources
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