End of an Era

Setting: Montana, USA

Time Period: Late Cretaceous, 66 million years ago

Plot Summary: Right before the end of the dinosaurs long and prosperous reign over Earth, they evolved some of the most iconic, powerful, and beautiful creatures ever to walk the Earth: the horned Triceratops, the hulking Edmontosaurus, the armored Ankylosaurus, and the terrifying Tyrannosaurus, the most famous dinosaur of all time. Dinosauria: Ascension, Domination, Downfall's final episode follows the final days of an old male Tyrannosaurus.

The Evidence

A formation that perfectly showcases the bizarre variety of animals in the Triassic is the Chinle Formation, specifically the Placerias Quarry in Arizona. This formation was the source of the vast majority of the things you see in "Dawn of an Era".

Camposaurus arizonensis

Camposaurus is the main focus and dinosaur representative of the episode. It was a member of one of the earliest and most prominent dinosaur groups of them all, the theropods. They are typically carnivorous and characterized by hollow bones, bipedalism and three-toed limbs. Later members of the group include the highly recognizable Spinosaurus and Tyrannosaurus rex, which were the top predators of their respective ecosystems (as explored in their upcoming respective episodes), as were many other large theropod predators that lived in the Jurassic and Cretaceous like them. This program showcases the humble beginnings of the theropods, and in turn, dinosaurs as a whole.

There are countless families of theropods. Camposaurus is part of a primitive theropod group that was very common in the Late Triassic and Early Jurassic, the coelophysids, which have distinctive long, slender skulls and light skeletons built for speed. Camposaurus in this documentary is heavily based upon its closest relative, rhodesiensis, due to Camposaurus' rather scant fossil material. We used Camposaurus in the episode instead of the better studied Coelophysis as it's the only known coelophysid from the Placerias Quarry, and it was important to set the episode in this quarry so the animal it's named after could appear in the episode (more on this later).