Mesozoic

The Mesozoic was an era of Earth history; best known for the dinosaurs.

Silurians were masters during the time, reigning over dinosaurs. (TV: The Silurians, Dinosaurs On a Spaceship, Deep Breath; PROSE: Blood Heat; AUDIO: The Silurian Candidate; GAME: Lost in Time)

The Cretaceous period was part of the Mesozoic era. The Seventh Doctor left Ace in the upper Cretaceous, around 75,000,000 BC. He returned to find her leading dinosaurs to destroy an alien colony being constructed by slave labour. (PROSE: Living in the Past)

Clockwork Repair Droids from the SS Marie Antoinette roamed Earth since the Mesozoic era until they including their leader known as the Half-Face Man fell to the newly-regenerated Twelfth Doctor in the 1890s. (TV: Deep Breath)