Stegosaurids were slow-moving plant-eating dinosaurs. They are characterised by having a small head and brain compared to their large body size. These dinosaurs moved On four legs With the highest point Of the spine above the larger legs at the rear. The main feature are the series Of bony plates running along the top of the dinosaur's back starting at the neck and going all the way doen the tail. The purpose of the plates Is not known, but may have been for display to attract other dinosaurs, or to scare attackers away. It is possible that skin covered the plates and their purpose was to control the dinosaur's body temperature.

Another common feature of these dinosaurs are the spikes at the end of the tail. These may have been used for defence but their purpose is not understood.

This dinosaur was first described by Othniel Charles Marsh, but because the bones were scattererd the proper arrangement of the bony plates was not initially understood. The first thoughts were that the plates lay flat on the back of the creature and this is why the name 'roof lizard' was given. It was later found from more examples found that the plates stood verticallly on the back.