Stegosaurus

Stegosaurus was a stegosaurid dinosaur, and the largest of its' kind, up to 7-9 meters long and possibly to 3-7 tons in weight. On average, though, it was smaller, around 7 m in length, and weighed 3-4 tons. It was a herbivore, as shown on Impossible Pictures, and may have been able to temporarily stand up on its hind legs to reach branches above its normal reach, as implied by R.T. Bakker. Other paleontologists have disagreed with that statement, however. Although Stegosaurus was a herbivore, they were very dangerous.

Stegosaurus' brain was really small for its overall body size - no bigger than a walnut which is what it was known for despite its hefty size and was sufficient for its needs, and that is why these dinosaurs had a secondary nervous center in their hips region, to better control the movement of their hind legs and formidable tail, which was armed with spikes up to 1.2 meters long. As long as baseball bats, these spikes were what make Stegosaurus so lethal. They could wheel those spikes with devastating effect and they were the primary weapon of the dinosaur against the large predatory theropod dinosaurs Stegosaurus coexisted with, such meat-eaters as Allosaurus and also Ceratosaurus (not shown in any Impossible Pictures features yet).

The 17 large plates on its back were arranged in a double row along the curved shape back of Stegosaurus and were primarily there for display not defense, which would be an odd place for armor. When faced with danger, Stegosaurus flushed blood into those plates, creating a frighting display of color, which could confuse and intimidate even a fully grown Allosaurus. Stegosaurus stand and fight with lethal spines.

Stegosaurus may have lived in herds, but there is no definite proof of it yet.

Eventually, stegosaurs died-out because the climate had changed by the middle of the Cretaceous, and new armored dinosaurs, the ankylosaurids (like the Polacanthus in the fourth episode of Walking with Dinosaurs) had appeared and outcompeted it.

In Walking with... series
Stegosaurus was a dinosaur featured in the second episode of Walking with dinosaurs, "Time of the Titans", as well as in "The Ballad of Big Al". In both instances, it played a secondary role, as one of key creatures of the Late Jurassic (152 MYA), where it interacted with the "stars", Diplodocus and Allosaurus, but only on occassion.