Planet Earth is filled with a dazzling diversity of life, but few animals can compete with the extinct dinosaurs for variety, size, and sheer magnificence. They roamed the earth way back in the ancient past and came in incredible shapes and sizes. Some of them were the most colossal creatures ever to have lived on land, while others were only the size of chickens. Some were fierce and had sharp claws and razor teeth, while others were harmless and docile. But how much do we know about these amazing creatures? Why did they die out? And what do their fossil traces tell us?