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The Jurassic Extinctions

The Jurassic Extinctions - The Cretaceous | The Cretaceous...

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The Jurassic Extinctions The Jurassic saw two minor mass extinctions. The first of these occurred about one- third of the way through the period, during the early Jurassic. This first Jurassic extinction affected approximately 80% of the bivalves as well as other shallow water organisms. At the close of the Jurassic, about 140 million years ago, a second minor mass extinction happened, affecting mostly the ammonoids, marine reptiles, bivalves and certain dinosaur groups such as the stegosaurs and the giant sauropods. Only one stegosaur escaped this extinction, Dravidosaurus , a small stegosaurid restricted to the Cretaceous of India (which was an island at that time). The causes of both of these extinctions are not clear.
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Unformatted text preview: The Cretaceous | The Cretaceous period, spanning the time interval from 144 to 65 million years ago, saw the final phases of the opening of the Atlantic Ocean, as well as the northward migration of India toward its collision with Asia during the Tertiary period of the Cenozoic era. The last of the major forms of plant life, the angiosperms, appeared near the beginning of the period. Dinosaurs continued their diversification, with the increasing dominance of the herbivorous ornithischians. The Cretaceous ended with the famous mass extinction that resulted in the extinction of the non-avian dinosaurs, the swimming reptiles, pterosaurs, ammonites and other creatures, nearly three-fourths of all life on Earth in fact....
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