Stegosaurus was a distinctive dinosaur that lived during the Late Jurassic period, around 155 to 150 million years ago. Measuring about 9 meters (30 feet) in length and weighing up to 5 metric tons, it is best known for its unique double row of large, bony plates along its back and the spikes on its tail, known as the thagomizer. Stegosaurus had a small head relative to its body size and a beak-like mouth for eating low-lying vegetation. Its fossils have been found primarily in North America, providing crucial insights into the anatomy and defensive adaptations of herbivorous dinosaurs.