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System	Series	Stage	Age (Ma)
Cretaceous	Lower	Berriasian	younger
Jurassic	Upper	Tithonian	145.5–150.8
		Kimmeridgian	150.8–155.7
		Oxfordian	155.7–161.2
	Middle	Callovian	161.2–164.7
		Bathonian	164.7–167.7
		Bajocian	167.7–171.6
		Aalenian	171.6–175.6
	Lower	Toarcian	175.6–183.0
		Pliensbachian	183.0–189.6
		Sinemurian	189.6–196.5
		Hettangian	196.5–199.6
Triassic	Upper	Rhaetian	older
Subdivision of the Jurassic system according to the IUGS, as of July 2009.

The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age age called the Dogger. This name was in the past also used to indicate the Middle Jurassic epoch itself, but is discouraged by the IUGS to distinguish between rock units and units of geological time.

Contents 1 Paleogeography 2 Life 2.1 Marine life 2.2 Terrestrial life 2.3 Flora

[edit] Paleogeography

Pangaea began to separate into Laurasia and Gondwana and the Atlantic Ocean formed. Tectonic activities are active on eastern Laurasia as the Cimmerian plate continues to collide with Laurasia's southern coast, completely closing the Paleo-Tethys Ocean. A subduction zone on the coast of western North America continues to create the Ancestral Rocky Mountains.

[edit] Life

[edit] Marine life

During this time, marine life (including ammonites and bivalves) flourished. Ichthyosaurs, although common, are reduced in diversity; while the top marine predators, the pliosaurs, grew to the size of killer whales and larger (e.g. Pliosaurus, Liopleurodon). Plesiosaurs became common at this time, and metriorhynchid crocodilians first appear.

[edit] Terrestrial life

New types of dinosaurs evolved on land (including Cetiosaurs, brachiosaurs, megalosaurs and hypsilophodonts).

Descendants of the therapsids, the cynodonts were still flourishing along with the dinosaurs even though they were shrew-sized; none exceeded the size of a badger. A group of cynodonts, the Trithelodonts were becoming rare and eventually became extinct at the end of this epoch. The Tritylodonts were still common though. Mammaliformes, who evolved from a group of cynodonts were also rare and less significant at this time. It was at this epoch that the "true" mammals evolved.

[edit] Flora

Conifers were dominant in the Middle Jurassic. Other plants, such as ginkgoes, cycads, and ferns were also common.

Jurassic period
Lower/Early Jurassic	Middle Jurassic	Upper/Late Jurassic
Hettangian | Sinemurian Pliensbachian | Toarcian	Aalenian | Bajocian Bathonian | Callovian	Oxfordian | Kimmeridgian Tithonian