Up to 12 metres long and up to 7 tonnes, Stegosaurus literally means "Covered Lizard" suggesting that its distinctive plates were a form of armour. Another theory, however, is that the plates were used as a heat sink, allowing the creatures to cool down rapidly, the plates being the perfect shape to dissipate heat in a breeze. It's difficult to know for certain what their purpose was and they could well have served a number of functions.
