Scientists Say: Jurassic

This word describes a time when dinosaurs dominated, from 200 million to 145 million years ago

Based on fossils, scientists have learned about large dinosaurs called Mamenchisaurus that would have been at home in the lush landscape of the Jurassic. Along with dinos, flying reptiles called pterosaurs dominated land ecosystems.

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Jurassic (adjective, “jur-RASS-sik”)

This word describes a time in Earth’s history. The Jurassic Period lasted from about 200 million to 145 million years ago. A mass extinction marks the start of the Jurassic. The event wiped out around three-quarters of species on Earth at that time. But during the Jurassic, life bounced back.

The fossil record shows that Jurassic oceans teemed with creatures. The seas held fish, microscopic plankton and hulking, swimming reptiles. On land, forests flourished. They contained ferns, palm-like cycads and conifers, such as pine. Birds and many insects evolved during the Jurassic. Early mammals existed, too. But pterosaurs, a group of flying reptiles, and dinosaurs dominated the land.

Some dinos were enormous. One called Brachiosaurus was as big as some buildings. This plant-eater grew up to 16 meters (52 feet) tall and 26 meters (85 feet) long. Not all dinos were huge, though. Tyrannosaurs were closer to the size of a deer. Some of these were ancestors of Tyrannosaurus rex, which didn’t live during the Jurassic. Fossils show that this most famous of dinosaurs evolved tens of millions of years after the Jurassic ended.

In a sentence

During the Jurassic, early snakes may have shared territory with dinosaurs.

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Carolyn Wilke is a staff writer at Science News for Students. She has a Ph.D. in environmental engineering. Carolyn enjoys writing about chemistry, microbes and the environment. She also loves playing with her cat.

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