The animal is getting longer and thinner. It can move more rapidly through the rocks. It is beginning to eat other animals. It reproduces sexually so that its many children differ from each other. The fastest and most ferocious become the parents of the next generation.
Adaptation Continues Over more millions of years the animal gets longer, thinner, and faster.
Its spines begin to support a band of skin that helps stability when it swims. It is beginning to be a predator, chasing down other small, moving life forms. It can see its prey moving in the water. This is a new species of strap swimmers. This chart shows the family tree of these animals and how they are related to each other.