Stegosaurus (stĕgəsôr´əs) [Gr.,=roof lizard], quadriped ornithischian dinosaur of the late Jurassic period. About 29 ft 6 in (9 m) long, it had short forelegs, four long bony spikes on a flexible tail, and two rows of upright triangular bony plates running along the back, which gave it a serrated profile. The function of the plates is debated. They may have acted as deterrents to predatory dinosaurs, but some scientists have suggested that they were not strong enough to have functioned that way. Other theories are that they helped regulate body temperature by dissipating heat or absorbing solar rays or that they helped members of the species recognize each other. The head of Stegosaurus was small, and the brain weighed about 2.5 oz (71 grams). The front of the mouth was beak-shaped; there were small leaf-shaped teeth in the cheek area. An herbivore, Stegosaurus, along with Ankylosaurus, belongs to the group of armored dinosaurs, Thyreophora. Fossil skeletons have been found in the Jurassic beds of Colorado, Utah, and Wyoming.
steg·o·saur / ˈstegəˌsôr/ (also stegosaurus / ˌstegəˈsôrəs/ ) • n. a small-headed quadrupedal herbivorous dinosaur (Stegosaurus and other genera, order Ornithischia) of the Jurassic and early Cretaceous periods, with a double row of large bony plates or spines along the back. ORIGIN: modern Latin, from Greek stegē ‘covering’ + sauros ‘lizard.’