Stegosaurus

Means: Roof Lizard

Period: Late Jurassic, about 155-150 million years ago

Region: Colorado, Utah and Wyoming, USA, Portugal, Europe

Stegosaurus was a slow-moving herbivorous quadruped and is perhaps one of the easiest dinosaurs to recognise thanks to its plates and tail spikes.  However, ever since the first fossils of this iconic dinosaur were found in 1877 Stegosaurus has caused much controversy.  For example, the famous American palaeontologist Othniel Charles Marsh, the first scientist to describe Stegosaurus, thought that the plates resembled the large flat bones that formed the shells of some types of prehistoric sea turtle.  Marsh suggested that Stegosaurus was an aquatic animal.  It was not until 1891, after the discovery of several more specimens that the first skeletal reconstruction of Stegosaurus was completed.  The hind limbs are much longer than the front limbs and it has been suggested that Stegosaurus could have reared up so it could feed on the branches of trees.

Scientists are still debating what the bony plates were used for and how exactly they were arranged along the back.  The plates are not attached to the spine but held in place with cartilage, tendons and muscles.  It is thought that the plates were arranged in two alternating rows running down the back with the largest plates (up to 1 metre high), located over the hips.  In this position the plates would have provided very little protection, it seems more likely that they played a role in species recognition or display behaviour.  The bony plates may also have helped maintain body temperature by acting as heat regulators.  The largest species measured around 9 m in length and weighed more than 3 tonnes.  Stegosaurus also had two pairs of spikes on the end of its tail.  These were probably defensive weapons.