Middle Jurassic

The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 161.5 million years ago. During this time, Earth looked very different from today. It had a warm climate and high sea levels that covered many land areas.

Fossils of land animals, such as dinosaurs, from the Middle Jurassic are not common. But important geological formations with fossils have been found in many places around the world. Examples include the Forest Marble Formation in England, the Kilmaluag Formation in Scotland, the Calcaire de Caen of France, the Daohugou Beds in China, the Itat Formation in Russia, the Tiourarén Formation of Niger, and the Isalo III Formation of western Madagascar.

Rocks from the Middle Jurassic were once called Dogger or Brown Jurassic in Europe until the 1980s. Studying these rocks and fossils helps scientists learn about how life changed and how Earth’s landscapes looked millions of years ago.

Paleogeography

During the Middle Jurassic Epoch, Pangaea began to split into Laurasia and Gondwana. The Atlantic Ocean started to form.

Eastern Laurasia was very active. The Cimmerian plate moved into Laurasia's southern edge. This closed the Paleo-Tethys Ocean completely.

A subduction zone along the coast of western North America helped build up the Ancestral Rocky Mountains. Subduction zones around Pangaea created new seabeds in the early Atlantic Ocean. They also formed mountain ranges like the Rockies and the Andes along the western coasts of North America, Central America, and South America.

Fauna

The Middle Jurassic was an exciting time for life on Earth. Many groups, like dinosaurs and mammals, grew and changed a lot during this period.

In the oceans, marine life such as ammonites and bivalves did well. Ichthyosaurs were common but not as many different types, while pliosaurs grew very big. Plesiosaurs became more common, and many kinds of fish lived in the Jurassic seas.

On land, many important groups of dinosaurs appeared. These included cetiosaurs, brachiosaurs, megalosaurs, and early ornithopods. Cynodonts, which came from the therapsids, were still around with the dinosaurs. Though mammals were small, they were found all over the world.

Flora

Conifers were the most common plants during the Middle Jurassic. Other plants, like ginkgoes, cycads, and ferns, were also found everywhere at this time.