Stegosaurus is the most famous dinosaur from a group of dinosaurs known as Stegosauria. They were all herbivores (plant eaters) and featured rows of unique bones that developed into plates and spines along their back and tail. The Stegosaurus was alive in the late Jurassic Period (around 150 million years ago). Stegosaurus fossils have been found in western North America and more recently in Portugal, indicating that they lived in Europe as well. In terms of size, the Stegosaurus was large and heavily built. On average, a fully grown Stegosaurus was around 9 meters (30ft) in length, 4 meters (14ft) in height, and up to nearly 5 metric tons in weight. Researchers believe that due to the nature of Stegosaurus legs, they had a maximum speed of around 7kph (5mph).