Evolution of whales and dolphins
 The first whale to exist is the pakicetus, it was named after it's discovery location in pakistan. It lived around 50 million years ago. The pakicetus lived in rivers, were there diet included small land animals that aproached the water or aquatic organisms found in the river, it was carnivore and it acted like a crocodile. The pakicetus had triangular teeth like a shark, orbits facing up to watch prey from underwater and ears formed only from the ectotympanic bone which is a characteristic only found in whales and dolphins.
The remingtonocetidae is the next evolutionary step, it lived around 43 to 49 million years ago. It is the first whale/dolphin ancester to loose its dependence on fresh water.  | Whales and dolphins are the only mammals in the sea to swim with there tails moving up to down instead of right to left like other sea creatures. They are also the only ones with a blowhole on there head for breathing. All of these features were passed down to them from there prehistoric ancesters. 
The ambulocetidae is the next evolutionary step of whales and dolphins. It lived around 49 million years ago. The ambulocetidae had the phisical appearence of a crocodile and was most likely amphibious. The ambulocetidae represents the transition phase between fresh water and marin habitat since they had salt in there fossilized teeth. Also, there eyes evolved from looking up to looking ahead.  The protocetus is the next evolutionary jump to becoming a whale/dolphin. It live approximatly 48 to 35 million years ago. It is slowly turning its legs into fins and loosing the back legs. The nose is also moving up the skull, slowly turning into a blowhole. |
After the protocetus, the ancesters of whales continued evolving, first loosing there back legs/fins then having the blowholeon there forehead and finally changing shape to finally become a modern whale.
