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Jurassic Period

The Jurassic ranges from 201 million to 145 million years ago, and features three major epochs: Early Jurassic, Middle Jurassic and Late Jurassic.

The Early Jurassic epoch spans from 201 million to 174 million years ago. The climate was much more humid than during the Triassic, and as a result, the world was warm and partially tropical, though possibly with short colder intervals. Plesiosaurs, ichthyosaurs and ammonites dominated the seas, while dinosaurs, pterysaurs and other reptiles dominated the land, with species such as Dilophosaurus at the apex. Crocodylomorphs evolved into aquatic forms, pushing the remaining large amphibians to near extinction. True mammals were present during the Jurassic but remained small, with average body masses of less than 10 kilograms (22 lb) until the end of the Cretaceous.

The Middle and Late Jurassic Epochs span from 174 million to 145 million years ago. Conifer savannahs made up a large portion of the world's forests. In the oceans, plesiosaurs were quite common, and ichthyosaurs were flourishing. The Late Jurassic Epoch spans from 163 million to 145 million years ago. The Late Jurassic featured a severe extinction of sauropods in northern continents, alongside many ichthyosaurs. However, the Jurassic-Cretaceous boundary did not strongly impact most forms of life.