The three ages
Earth history is divided into chunks of time. Dinosaurs and other prehistoric reptiles were the dominant animals for about 185 million years during the Mesozoic era. It lasted from 250 million years ago to 65 million years ago, and contained three periods called the Triassic, Jurassic and Cretaceous.
Triassic period (245 million years ago)
The first dinosaurs such as Coelophosis and Euskelosaurus appeared.
Jurassic period (208 million years ago)
Dinosaurs included diplodocus, stegosaurus and brachiosaurus.
Cretaceous period (144 million years ago)
Dinosaurs died out towards the end of this period.