The Kentrosaurus, whose name means Spiked Lizard, was a medium sized stegosaur with a double row of blade like plates running down its back and with a tail topped by paired spikes for its entire length. It was an herbivore who roamed during the Upper Jurassic period. Paleontologists have estimated it at 15 feet long and 1.1 ton. Its longest spikes were at the tail and used to defend itself. It is estimated that it could swing its tail about 30 mph.