Temporal range: Lower Jurassic, 196–194 mya
Scelidosaurus was a genus of thyreophorans, a lightly plated, herbivorous dinosaur about 4 metres long. It lived during the Lower Jurassic, 208 to 194 million years ago. Its fossils have been found in both England and in Arizona, in the United States.
Scelidosaurus has been called the earliest complete dinosaur. This and related genera have been found on three continents.
A full-grown Scelidosaurus was rather small, compared to most other dinosaurs. Some scientists have estimated a length of 4 metres (13 ft). Scelidosaurus was quadrupedal, with the hindlimbs considerably longer than the forelimbs. It may have reared up on its hind legs to browse on foliage from trees, but its forefeet were as large as its hind feet, indicating a mostly quadrupedal posture.
Scelidosaurus and its Jurassic relatives were herbivorous. However, while other ornithischians had teeth capable of grinding plant material, Scelidosaurus had smaller, less complex teeth and a jaw capable of only simple up-and-down jaw movements. In this aspect, they resembled the stegosaurids, which also bore primitive teeth and simple jaws. Also like stegosaurs, they may have swallowed gastroliths to aid processing of food (because of the lack of chewing ability), in the same manner used by modern birds and crocodiles. Their diet would have consisted of leaved plants or fruits, as grasses did not evolve until after Scelidosaurus had become extinct.
- Norman, David 2001. Scelidosaurus, the earliest complete dinosaur. In The armored dinosaurs, pp 3-24. Bloomington: Indiana University Press. ISBN 0253339642
- Serano P.C. 1986. Phylogeny of the bird-hipped dinosaurs (Order Ornithischia). National Geographic Research 2, 234–256.
- Lambert D 1993. The ultimate dinosaur book. Dorling Kindersley, New York, 110-113. ISBN 1-56458-304-X
- Galton PM, Upchurch P (2004). "Stegosauria". In Weishampel DB, Dodson P, Osmólska H. The Dinosauria (2nd Edition. University of California Press. p. 361. ISBN 0-520-24209-2.
- Stegosaurs Jacobson RJ. Dinosaur and vertebrate paleontology information. Retrieved 2007-02-11.