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The Earth is over 4,000 million years old, and its history is divided by scientists into eras. Each era is further subdivided into periods. The era during which dinosaurs first appeared, and at the end of which they became extinct, sometimes popularly known as "The Age of Reptiles", is known as the Mesozoic Era. The Mesozoic Era lasted from 248 million to 65 million years ago, and is subdivided into three separate periods - the Triassic period, the Jurassic period, and the Cretaceous period.

The Jurassic period is the middle period of the dinosaur's reign, and lasted from about 213 million to 144 million years ago. During the earlier Triassic period, dinosaurs had been gradually displacing the last mammal-like reptiles as the dominant land creatures, but by the Jurassic, their dominance was compete. Furthermore, it was during the Jurassic that many of the more familiar types of dinosaurs evolved, including the great sauropod dinosaurs such as Apatosaurus (also known as "Brontosaurus"), Brachiosaurus and Diplodocus, some of the early armored dinosaurs such as Kentrosaurus and Stegosaurus, as well as predators such as Allosaurus and Ceratosaurus.

Feathers probably also first evolved during the Jurassic, and it is thought that birds (which also appeared in the Jurassic) probably evolved from a feathered dinosaur. Additionally, pterosaurs were found in the skies, and there were also a wide variety of large marine reptiles living in the seas.

Prior to the Jurassic, the Earth's continents had all been combined into one super-continent, known as Pangaea, but by the mid-Jurassic Pangaea had begun to break into two smaller supercontients: Laurasia (formed from Asia, Europe and North America), and Gondwanaland (formed from South America, Africa, Australia, Antarctica and India). Flowering plants had not yet evolved, and instead Laurasia and Gondwanaland were home to plants such as conifers, cycads, and ferns.

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