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Strong evidence suggests that a huge asteroid impact caused the mass dinosaur extinction 66 million years ago. Image by Donald E Davis courtesy of NASA/JPL-Caltech, via Wikimedia Commons

What killed the dinosaurs?

The end of the Cretaceous Period saw one of the most dramatic mass extinctions Earth has ever seen. Find out what brought about the end of the dinosaurs and many other animals too.

The fossil record shows that for the first 175 million years of their existence, dinosaurs took on a huge variety of forms as the environment changed and new species evolved that were suited to these new conditions. Dinosaurs that failed to adapt went extinct.

But then 66 million years ago, over a relatively short time, dinosaurs disappeared completely (except for birds). Many other animals also died out, including pterosaurs, large marine reptiles, and ammonites.

Although the number of dinosaur species was already declining, this suggests a sudden catastrophic event sealed their fate - something that caused unfavourable changes to the environment to occur more quickly than dinosaurs and other creatures could adapt.

What caused the Cretaceous extinction?

The exact nature of this catastrophic event is still open to scientific debate. Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth's climate that happened over millions of years.

Whatever the causes, the huge extinction that ended the age of the dinosaur left gaps in ecosystems around the world. These were subsequently filled by the only dinosaurs to survive - birds - and mammals, both of which went on to evolve rapidly.

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