Definition:
Mammals are animals in the Class Mammalia. All mammals are chordates, but not all chordates are mammals!
There are several characteristics common to all mammals, including:
- They are endothermic.
- They give birth to live young (all except the platypus and echidna, which lay eggs).
- They nurse their young, and all females have mammary glands.
- They have hair.
Examples of marine mammals include: cetaceans, pinnipeds, and sirenians.
