Why do most marine mammals have horizontal tails, while other marine life tend to have vertical tails?

Question

Why do most marine mammals have horizontal tails, while other marine life tend to have vertical tails?

In: 75

Answer 1

The main reason that sea mammals tails are different from fish is that mammals breath air. The default movement of a whale for example is to go up to get air and go back down, while a fish primarily only has to move side-to-side. Whales and dolphins tails evolved from a typical straight tail and their legs became smaller and smaller until they were not longer present.