During the Middle Jurassic Epoch, Pangaea began to separate into Laurasia and Gondwana, and the Atlantic Ocean formed.

A subduction zone on the coast of western North America continued to create the Ancestral Rocky Mountains.Significant subduction zones were active along practically all of the continental edges surrounding Pangea, as well as in southern Tibet, southeastern Europe, and other locations, to allow the formation of fresh seabed in the proto-Atlantic Ocean.

[citation needed] The Middle Jurassic is one of the key periods in the history of life on Earth.

Ichthyosaurs, although common, are reduced in diversity; the top marine predators, the pliosaurs, grew to the size of killer whales and larger (e.g. Pliosaurus, Liopleurodon).

[citation needed] Many of the major groups of dinosaurs emerged during the Middle Jurassic, (including cetiosaurs, brachiosaurs, megalosaurs and primitive ornithopods).