Middle Jurassic

The Middle Jurassic is the second geological epoch in the Jurassic. It began 174.1 million years ago, and ended at 163.5 million years ago.
In the Middle Jurassic, Pangaea began to split apart. It began to separate into Laurasia and Gondwana, and the Atlantic Ocean formed. Tectonic activities closed the Paleo-Tethys Ocean. A subduction zone on the coast of western North America continues to create the ancestral Rocky Mountains.
Life of the epoch.
Marine life.
During this time, marine life (including ammonites and bivalves) flourished. Ichthyosaurs, although common, are reduced in diversity. A type of crocodilians first appeared.
Plesiosaurs became common at this time. The top marine predators, the pliosaurs, grew to the size of killer whales and larger e.g. "Pliosaurus", "Liopleurodon".
Terrestrial life.
New types of dinosaurs evolved on land. "Cetiosaurus" was an early sauropod found in England in the mid-19th century.
The environment in which "Cetiosaurus" lived was floodplain and open woodland. Brachiosaurs and "Megalosaurus" also lived in this environment.
The cynodont therapsids flourished with the dinosaurs, but they were only shrew-sized. None grew larger than a badger. One group of cynodonts, the Trithelodonts were becoming rare and eventually became extinct at the end of this epoch. The Tritylodonts were still common, though. In this epoch "true" mammals evolved from a group of cynodonts.
Flora.
Conifers were dominant in the Middle Jurassic. Other plants, such as ginkgoes, cycads, and ferns were also common. These are the trees which the large herbivores ate.