Dating from 245-66 mya, the Mesozoic (Middle Animals) Era, the Age of Reptiles, marks the beginning of land animals and plants. During this Era, gymnosperms first evolved, invading deep into new territory away from shores where water was plentiful. As these new plants moved inland, animals soon followed.

Mammals evolved in this era, but were relatively small and insignificant compared to reptiles. The dinosaurs evolved, flourished in every habitat on land, then re-invaded the oceans. The first birds also appeared at this time.

Pangaea began to break up during the Mesozoic Era, resulting in a worldwide rise in sea level and much milder climates.

The Mesozoic ended as the dominant dinosaurs died. In fact, most reptiles died, as well as many nonreptiles. The most widely accepted theory is that the extinction occurred after a meteor struck the Earth, changing the environment.

The Mesozoic Era is split into three periods: Triassic, Jurassic, and Cretaceous. Click on the links below to find out more about these periods.