Extinction of Dinosaurs

65 mya a disaster happened which eradicated all dinosaurs and opened the door for the diversification of the mammals. Astonishingly, we are still not sure why all the dinosaurs and many other groups of animals and plants became extinct around this time.

Meteorite Theory

The most popular theory is that a mountain-sized meteorite hit the Earth, throwing up a thick cloud of dust and causing tidal waves and global forest fires. The dust hid the Sun. This might have killed many plants, which need light to live. It might also have cooled the Earth and so killed the dinosaurs which, being unable to keep themselves warm, might have stopped moving and so starved.

There is much doubt about why these extinctions happened. At any rate the dinosaurs, then the most important animals, did die out, leaving lots of life-styles free for mammals to evolve into.