Cretaceous

The Cretaceous was a period in early Earth history in which the dinosaurs, such as tsintaosaurus, dsungaripterus, protoceratops, velociraptor, ankylosaurs, tyrannosaurs, bactrosaurs and Alioramus, thrived.

Once, the Seventh Doctor and Ace took into account a visit during the upper Cretaceous, considered a "very good time for dinosaurs". (TV: The Happiness Patrol) Eventually, the Doctor arrived in Mongolia during the Cretaceous period to pick up Ace, whom he had dropped off there. Along the way he encountered a pit of dholes and an alien slave who had escaped from a nearby construction site. Ace arrived with a herd of dinosaurs to trample the site, destroying it and freeing the slaves. (PROSE: Living in the Past)

In another occasion, the Seventh Doctor guessed the Rani had popped back to the Cretaceous age to collect embryos of the Tyrannosaurus rex. (TV: The Mark of the Rani) Later, the Time Lady meant to use a Time Manipulator to come back to this age and avert the extinction of the dinosaurs. (TV: Time and the Rani)