Evolution of Cetaceans

Evolution Of Cetaceans

The cetaceans (whales, dolphins and porpoises) are marine mammal descendants of land mammals. Their terrestrial origins are indicated by:

• Their need to breathe air from the surface;
• The bones of their fins, which resemble the limbs of land mammals
• The vertical movement of their spines, characteristic more of a running mammal than of the horizontal movement of fish.

The question of how a group of land mammals became adapted to aquatic life was a mystery until discoveries starting in the late 1970s in Pakistan revealed several stages in the transition of cetaceans from land to sea.