Stegosaurus was one of the earliest dinosaurs. It was the
first of the armored, or plated, dinosaurs. A row of 20
tough, bony plates grew along this plant eater's back and tail.
The plates helped heat and cool the animal's body by either
absorbing the sun's heat or reflecting the sun's heat away from
the animal. At the end of its tail, Stegosaurus had two
pairs of sharp spikes to use as weapons.