Ceratosaurus

Ceratosaurus Temporal range: Late Jurassic, 153–148 Ma PreЄ Є O S D C P T J K Pg N ↓
Mounted cast of a juvenile skeleton, Dinosaur Discovery Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Family:	†Ceratosauridae
Genus:	†Ceratosaurus Marsh, 1884
Species
†C. nasicornis Marsh, 1884 (type) †?C. dentisulcatus Madsen & Welles, 2000 †?C. magnicornis Madsen & Welles, 2000
Synonyms
Megalosaurus nasicornis (Marsh, 1884 [originally Ceratosaurus])

Ceratosaurus /ˌsɛrətoʊˈsɔːrəs/ (from Greek κερας/κερατος, keras/keratos meaning "horn" and σαυρος/sauros meaning "lizard"), was a large predatory theropod dinosaur from the Late Jurassic Period (Kimmeridgian to Tithonian), found in the Morrison Formation of North America, and the Lourinhã Formation of Portugal (and possibly the Tendaguru Formation in Tanzania). It was characterized by large jaws with blade-like teeth, a large, blade-like horn on the snout and a pair of hornlets over the eyes. The forelimbs were powerfully built but very short. The bones of the sacrum were fused (synsacrum) and the pelvic bones were fused together and to this structure (i.e. similar to modern birds). A row of small osteoderms was present down the middle of the back.

Ceratosaurus, at first glance, looked like a fairly typical theropod, however its skull was quite large in proportion to the rest of its body, and large nasal and brow horns and possessed a prominent nose horn formed from protuberances of the nasal bones. In addition to the large nasal horn, Ceratosaurus possessed smaller hornlike ridges in front of each eye, similar to those of Allosaurus, these ridges were formed by enlargement of the lacrimal bones. Uniquely among theropods, Ceratosaurus possessed dermal armor, in the form of small osteoderms running down the middle of its back. Its tail comprised about half of the body's total length and was thin and flexible with high vertebral spines.