Late Jurassic – 150 million years ago
Western North America and Europe(Portugal)
Whether battling its own kind or predators, Stegosaurus could swing its two pairs of tail spikes (each up to four feet long) as awesome defensive weapons. The 17 bony dorsal plates arranged alternately along its spine may have served as armor, a mating display, heat regulation, or all three. These plates may have allowed Stegosaurus to appear larger, thereby discouraging enemy attack.