Permian period

The Permian was a period in Earth's history. It was dominated by a harsh, arid and volcanic environment, and it was ruled by reptiles, most of which were the ancestors of mammals.

Real life
The Permian period lasted from approximately 299 to 252 million years ago. During the Permian, the world was dominated by a single supercontinent surrounded by oceans, and the majority of the land was dominated by arid desert. The weather was extreme with very, very cold winters and very, very hot summers. At the end of the Permian there was a mass extinction which wiped out 95% of life. Due to the arid conditions, reptiles rose to dominance in the Permian. The Permian ended with largest-scale mass extinction event in Earth's history, with 90% of marine life and 70% of terrestrial life dying out.

Trivia
The Permian was the first time period other than the present to appear in the Primeval franchise.