mammal

An individual of the class Mammalia, a division of vertebrates, including all that possess hair and suckle their young.

• eutherian m's — true placental mammals which develop chorion, amnion, yolk sac and allantois, all of which contribute to the placenta. Called also placental mammals.
• metatherian m's — marsupials including kangaroos, opossums which are born after a brief period of development and spend a long time being nurtured by the mother, usually in a pouch or marsupium.
• placental m. — see eutherian mammals (above).
• prototherian m's — monotremes, the egg-laying mammals.