220 million years ago, Late Triassic (Arizona)Filming location: New Caledonia

A female Coelophysis is shown stalking a herd of dicynodonts called Placerias (a giant synapsid or mammal-like reptile), looking for weak members to prey upon. A male Thrinaxodon is shown downstream, returning to his burrow from the river. The last focus of the episode is a female rauisuchian Postosuchus (one of the largest carnivores alive in the Triassic) who is first shown attacking a Placeriasherd and bites one of the members, driving the rest of the herd to retreat and leave the wounded and weakened member of the group to the carnivore. Early pterosaurs called Peteinosaurus are depicted feeding on dragonflies and cooling themselves in what little water is present during the drought. Still searching for food, the Coelophysis are shown discovering the Thrinaxodon burrow (and are initially frightened away by the male when it emerges). Eventually, an inquisitive Thrinaxodon pup follows the father to the entrance and is eaten by the female Ceolophysis before he can drive the predator away. At night, the pair of Thrinaxodon are shown eating their remaining young, then moving away, while during the day, the Coelophysis work to expose the nest.

The female Postosuchus is later shown to have been wounded by the Placerias in a previous attack (which left her with a tusk wound on her thigh), and after being unable to successfully hunt another member of the Placerias herd she is beaten out of her territory by a rival male Postosuchus. Wounded, sick and without a territory, the female dies and is eaten by a pack of Coelophysis. As the dry season continues however, food becomes scarce and extreme measures are taken by all animals. The Placerias herd embarks on a trek through parched wasteland in search of water, while the Coelophysis start killing and cannibalising their young. The male Thrinaxodon also resorts to hunting baby Coelophysis during the night. Finally, the wet season comes, and the majority of theCoelophysis have survived (including the female), along with the Thrinaxodon pair, who have a new clutch of eggs. The episode ends with the arrival of a migrating herd of the prosauropod Plateosaurus, foreshadowing the future dominance of the giant sauropods after the Triassic-Jurassic extinction event.

Animals Coelophysis · Thrinaxodon (identified as Cynodont) · Placerias · Postosuchus · Peteinosaurus · Plateosaurus · Lungfish ·Dragonflies