Stegosaurus: The Jurassic plant-eater with a double row of plates

Stegosaurus is one of the easiest dinosaurs in the museum to spot: it carries a double row of plates along its back and a cluster of spikes at the end of its tail. It was a plant-eating stegosaur that lived during the Late Jurassic. Let's meet it slowly, together.

Its body

The most striking feature is the row of plates along its back — they look a little like a line of gentle hills. These plates were not fixed to the skeleton. Instead, they grew out of the skin, like large scales padded with a sheath. Their exact shape, size and arrangement differ between specimens, and scientists still debate what they were for. They might have helped control temperature, or been used to show off between individuals, or made the animal look bigger — none of these ideas is settled.

The head is small compared with the body, with a broad beak at the front for cropping low plants. The hind legs are longer than the front legs, so the animal moved in a steady, balanced way. The thick spikes at the end of the tail are often thought of as defence, or as tools for fighting between individuals, but that is still an interpretation rather than a proven fact.

Where it lived and what it ate

Stegosaurus browsed on low ferns, cycads and shrubs. Long hip muscles and shorter front legs made it easy to reach the ground to feed. It lived in the Late Jurassic, when western North America held broad, damp floodplains full of plants that plant-eating dinosaurs could eat.

Where its fossils were found

Most Stegosaurus fossils come from western North America, especially the Morrison Formation in the United States — one of the most important fields for Late Jurassic dinosaurs, where many other iconic species were also discovered.

What the fossils tell us — and what they do not

Fossils preserve the skeleton, the size and the rough shape of the body, but soft parts — the colour of the skin, whether the plates were covered in horn, what noise the animal made — almost never survive. So the colours, the exact shape of the plates and the way the tail spikes were used in this exhibit are evidence-informed artistic reconstructions, not confirmed facts.

A note for grown-ups

When you observe Stegosaurus with a child, you could ask: "Which familiar things do the plates remind you of?" That question helps a child notice features — and it also shows how palaeontologists work, slowly building a picture of an animal from the clues in its fossils. Please bear in mind that the colours and movements on the museum stage are artistic reconstructions, not direct evidence left behind by the fossils.