Answer:Cretaceous Period. The Cretaceous is the Phanerozoic's longest period, and the last period the Mesozoic. It spans from 145 million to 66 million years ago, and is divided into two epochs: Early Cretaceous, and Late Cretaceous.
Explanation:Eons are the largest intervals of geologic time and are hundreds of millions of years in duration. In the time scale above you can see the Phanerozoic Eon is the most recent eon and began more than 500 million years ago. Eons are divided into smaller time intervals known as eras.