What are dinosaurs?

Dinosaurs is the name given to a huge number of different reptiles that lived on planet earth for many years. The word dinosaur means terrible lizard. The oldest dinosaurs arrived on earth approximately 230 million years ago. There were many different shapes and sizes of dinosaurs. Some dinosaurs were as big as 30 metres long and 15 metres high, however, others might have been smaller than a chicken. The main reason why we have discovered dinosaurs is thanks to the work of archaeologists. Many fossils of dinosaurs have been found in loads of different countries since they have been extinct, however, not all these were found at once. It has taken many years of scrutinizing investigation to find out what we know about dinosaurs today.