Jurassic Period

The Jurassic is a geologic period that extends from 201 million to 145 million years ago, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. It is named after the Jura mountains on the border between Switzerland and France, where rocks of this age were first studied.

The start of the period was marked by a major extinction event which profoundly affected life both on land and in the oceans. At least half of the species known to have lived on Earth at the time were extinct, vacating ecological niches and allowing the dinosaurs to assume their dominant role in the Jurassic.

During the Jurassic Period, the supercontinent consisting of all of Earth's land masses split apart into two smaller supercontinents. The northern part would eventually form North America and Eurasia. The southern part was drifting into an eastern segment that would form Antarctica, Madagascar, India and Australia, and a western segment that would form Africa and South America. The rifting of land created more coastlines and shifted the continental climate from dry to humid. As a result, many of the arid deserts of the Triassic were replaced by lush rainforests, providing the grounds for a golden age of large herbivorous dinosaurs. These in turn were preyed upon by matching predators of their kind, and the terrestrial world flourished. Early mammals were also developing and diversifying. And the first birds appeared, having evolved from a branch of dinosaurs.

In the Jurassic seas, life was teeming too. There were abundant coral reefs, fish, fishlike reptiles, giant marine crocodiles, squid, sharks, rays. The oceans were dominated by maritime monsters like Ichtiosaurus and Plesiosaurus, while Pterosaurus were dominant flying vertebrates in the air.

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