Marine mammals are a group of roughly 120 species of ocean-dwelling mammals or depend on the ocean for food. Marine mammals evolved from land dwelling ancestors, but not all from the same ancestor, Cetaceans and Sirenians are thought to descendant from an ungulate ancestor, while the otter, pinnipeds and polar bear are descended from a caniform ancestor. They have adapted to the life in the sea and share some characteristics, like a generally large size, hydrodynamic body shapes, appendages and several adaptations for controlling warmth. Many populations of mammals living in the water are vulnerable or endangered throughout a history of commercial exploitation for blubber, meat, ivory and fur. Mammals living in the water breathe air, while for example fish extract oxygen from the water through their gills. Did you know polar bears can swim 74 kilometers in a day?

Examples are:False Killer Whale,Chinese white dolphin,Fraser's dolphin,Bridled dolphin,Atlantic white-sided dolphin,Atlantic spinner dolphin,White-beaked dolphin,Euphrosyne dolphin,Blackchin dolphin,Atlantic spotted dolphin,Hourglass dolphin,Bowhead whale,Long-beaked dolphin,Pacific white-sided dolphin.

Of course I know there should be much more...But that's all folks!

By the way,i'm Celine,signing off.