Dinosaurs are animals that appeared on Earth 230 million years ago, before mysteriously disappearing 65 million years ago. Nobody knows why this happend, but scientists have two main theories to explain it. Brachiosaurus was one of the tallest and heaviest dinosaurs. It grew to about 12 m tall and weighed about 89 tonnes. Compsognathus was one of the smallest. It was about 60 cm long and was a fast-running hunter. Teeth fossils reveal whether dinosaur was plant eater or meat eater. You can learn about these two theories and other interesting facts in the centre.