Tyrannosaurs are, by some margin, the most famous dinosaurs in the world. Popular among children and adults alike, it is the only dinosaur many people can name. The Tyrannosaurus was an impressive beast, it topped ten tons, was more than forty feet (fifteen meters) long, and had the largest head and most powerful bite of any land animal, ever. The Tyrannosaurus and other tyrannosaurs are fascinating animals and perhaps the best-studied of all dinosaur groups. They started small, just a couple of yards long, and over the course of 70 million years evolved into giant, meat-slicing bone crushers.