Stegosaurus lived about 150 million years ago in what is now the western part of the USA. It lived alongside some of the most famous dinosaurs, such as Diplodocus, Brontosaurus and the meat-eater Allosaurus, which was probably its major predator. Stegosaurus was a plant-eating dinosaur that probably ate woody ferns and soft vegetation; flowering plants and grasses had not yet evolved.
The most famous feature of Stegosaurus is the row of bony plates and spikes that ran down its back to the end of its tail. The plates may have been used for display, perhaps to make the animal look bigger and more scary than it really was: it couldn’t run away from predators, because its limbs suggest it could only have moved slowly, so perhaps it used the plates in defensive displays instead. Stegosaurus could have swung its tail and inflicted wounds on the legs and bodies of predators with its fearsome spikes.
Stegosaurus is just one of a group of stegosaurian dinosaurs which lived from about 165 million years ago until about 100 million years ago. Stegosaur fossils are known from the UK, France, Portugal and Spain in Europe. They have been found in abundance in Jurassic rocks in China, and there are also some stegosaurs from Morocco, Tanzania and South Africa. They were probably present in South America as well, although the fossils there are very fragmentary and we don’t know much about them yet. So far, no stegosaurs have been found in Australia, although fossil footprints that were probably made by stegosaurs suggest they lived there.
Although stegosaurs are some of the most famous and easily recognisable dinosaurs, their fossils are surprisingly rare, and we don’t know as much about them as we do about dinosaurs that lived later, in the Cretaceous period. There are only around four or five complete stegosaur skeletons known from anywhere in the world.
Susannah Maidment is a dinosaur researcher and curator at the Natural History Museum, London, UK. Susannah leads a research group that studies the bird-hipped ‘ornithischian’ dinosaurs to try to understand how they are related to each other and how they lived their lives.
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