Tyrannosaurus Rex 42 feet 18 feet 5-7 tons 25 mph Teeth Though the Tyrannosaurus had many different sizes of teeth, all were razor sharp and some grew to lengths of 9-13 inches. Broken teeth were replaced frequently by newer teeth. The powerful jaw exerted in excess of 3000 pounds of pressure! Osborn 1905 Canada Alberta The Tyrannosaurus Rex was the king of the terrible lizards. Though many now believe it was a hunter and a scavenger it is no less fearsome. Stegosaurus Armatus 25-40 feet 14 feet 2-4 tons Spikes The Stegosaurus had two long rows of armor along its back. At the end of its tail four large spikes were an excellent defense. Marsh 1877 United States Colorado The Stegosaurus Armatus was, perhaps, the most heavily armored of all dinosaurs. It is very possible though that it was not very smart, it's brain is believed to have been the size of a walnut! Gallimimus Bullatus 18 feet 8 feet 1000 pounds 35-60 mph Osmólska Roniewicz Barsbold 1972 Mongolia Nemegtskaya Svita The Gallimimus Bullatus, or Chicken Mimic was very fast, perhaps even the fastest of all dinosaurs.