Dinosaur Extinction Asteroid

Friday, July 9, 2010

Dinosaur Extinction and the Rise of Mammals

At the end of the Cretaceous, 65 million years ago, not only did the dinosaurs disappear completely, but so did flying reptiles (pterosaurs), and marine reptiles (ichthyosaurs and plesiosaurs). In fact, between 60 and 80% of all animal species, including many marine forms, disappeared. Most turtles, crocodiles and primitive birds also disappeared but some survived to give rise to modern forms.

There have been numerous theories to account for the extinction of dinosaurs. But during the 1980's strong evidence was obtained to support the idea, originally proposed by Luis Alvarez, that a global catastrophe, caused by the impact of an asteroid, comet or meteorite, was responsible. Enormous amounts of debris would have been thrown into the atmosphere, making the Earth so cold and dark that cold-blooded animals like dinosaurs were unable to survive.


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