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Jurassic
Northern Madagascar
Ammonites were a very successful life form. They once existed all over the earth and evolved into many different species. They disappeared sixty million years ago at the same time that the dinosaurs disappeared. It is thought that their demise, like that of the dinosaurs, was due to one or more asteroids falling into the sea. Asteroids could have raised the ocean's temperature, increased its salt content, or covered the ocean surface with a fine dust that would have interfered with oxygen absorption, and prevented much of the sunlight from reaching the earth, thereby killing many plants.