Kingdom = animalia Pylum = chordata class = mammalia
Modern mammals are divided into three sub-classes:
Mammals are endothermic, have hair, a four-chambered heart, an single lower jaw, suckle their young, and are heterodonts. Not all mammals bear live young. Go read that bit about the Prototheria again.
Mam"mal (?), n.; pl. Mammals (#). [L. mammalis belonging to the breast, fr. mamma the breast or pap: cf. F. mammal.] Zool.
One of the Mammalia.
Age of mammals. See under Age, n., 8.
© Webster 1913.
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