Stegosaurus
Although not always able to outrun its carnivorous foes, the 21-foot-long, two-ton Stegosaurus always had a final line of defense, its bony plated back and spiny tail.
If cornered or outmaneuvered by a larger enemy, the Stegosaurus’ back plates afforded some protection while the four to eight spikes on the end of its tail (which grew as long as four feet)F made it dangerous for any foe to approach too carelessly.
Scientists believe the vertical plates may have been for warming or cooling the body, picking up heat from the sun when the weather was cool to the Stegosaurus, or giving off heat when it was too hot.