The year is 65.5 million BC, and the time is 11:59pm for the dinosaurs. Volcanic activity has begun to choke the land, and dinosaurs are suffering. Few eggs are hatching, poisoned by the toxins in the air. Dinosaurs are on the decline, while mammals are thriving. The pterosaurs are all but gone, replaced by birds, and a massive asteroid is on its final journey to Earth. In this world, the most infamous carnivore stalks the land, the mighty Tyrannosaurus.

In the mid-Cretaceous, Australia, Antarctica, and South America are still connected in one super continent. This is a time when the South Pole is a huge polar forest, where for five months of the year, the sun never sets. The Antarctic forests are a land which time forgot, where allosaurs still prowl the forests and ancient amphibians still hunt along the river banks. We fellow a year in the life of a clan of small dinosaurs, Leaellynsaura, and their struggle to survive in this unique environment.

Reptiles not only rule the seas, but the skies as well. This is the time of the pterosaurs, flying reptiles that dominate the Cretaceous skies. And at this point, none is as large as the massive Ornithocheirus, the largest pterosaur at the time. We follow the final days of one such Ornithocheirus as he makes his way to the mating grounds, soaring over the lands ruled by dinosaurs.

Dinosaurs may rule the land, but it's a different story in the oceans. Marine reptiles dominate the seas. A school of female Opthalmasaurus are moving into the reefs around the northern Tethys Sea to give birth. Once born, the young ichthyosaurs must dodge sharks, plesiosaurs like Cryptoclydus, and the monsterous pliosaur Liopleurodon, the largest carnivore ever.

It is the late Jurassic, and dinosaurs rule the land. At the height of this reign, sauropods are the dominate herbivore on Earth. We follow the life of one sauropod, a Diplodocus, from hatchling to sub-adult, and the challenges she faces in her world.

It is the mid-Triassic period, an the sun is setting on the age of reptiles. Once the most dominant lifeform on the planet, reptiles are now represented by only a few species. But as the age of reptiles wanes, new animals are on the rise, and among them, the first members of a new dynasty: the dinosaurs.