Why are birds the only surviving dinosaurs?
The story of the disappearance of dinosaurs is a famous one. Less familiar is the tale of the dinosaurs that were left behind.
What is it about birds that allowed them to survive when all other dinosaurs died out? Watch our animation.
By the start of the Jurassic Period, 201 million years ago, dinosaurs had become the global superstars of the animal kingdom.
There were lots of them - and lots of different species - and they held the top carnivore and top herbivore spots in food chains.
The beginning of birds
Birds evolved from a group of meat-eating dinosaurs called theropods. That's the same group that Tyrannosaurus rex belonged to, although birds evolved from small theropods, not huge ones like T. rex.
The oldest bird fossils are about 150 million years old. These ancient birds looked quite a lot like small, feathered dinosaurs and they had much in common. Their mouths still contained sharp teeth. But over time, birds lost their teeth and evolved beaks. Can you imagine coming face-to-face with a toothy pigeon?
The end of dinosaurs' rule: the Cretaceous extinction
After more than 140 million years in charge, the reign of the dinosaurs came to an abrupt end when a huge asteroid strike and massive volcanic eruptions caused disastrous changes to the environment. Most dinosaurs went extinct. Only birds remained.
Over the next 66 million years, birds evolved in many ways, which enabled them to survive in lots of different habitats. Today there are at least 11,000 bird species.
But with such a close relationship to the extinct dinosaurs, why did birds survive?
The answer probably lies in a combination of things: their small size, the fact they can eat a lot of different foods and their ability to fly.
Watch the animation to find out more.