The Jurassic period follows the Triassic on the geological time scale. Though the dinosaurs had their origins and approximately 25 million years of evolution in the Triassic period, it was not until the Jurassic that this group really blossomed. This was the time when the giant, herbivorous sauropods like Apatosaurus roamed the land; when plated dinosaurs like Stegosaurus first appeared; and when large carnivorous species like Allosaurus preyed on the other dinosaurs. It was also when Archaeopteryx—a creature that many paleontologists consider to be one of the first ancestors of birds—flew through the air.

The name Jurassic comes from the Jura mountain range, a chain of mountains that straddle the border between France and Switzerland. It was there that the first Jurassic period sedimentary rock and accompanying fossils were found. The Jurassic is the second of three periods (the first is the Triassic and the last is the Cretaceous) making up the Mesozoic era.