Ceratosaurus nasicornis
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Ceratosaurus Temporal range: Late Jurassic, 153–148 Ma |
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| Mounted cast of a juvenile skeleton, Dinosaur Discovery Museum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Order: | Saurischia |
| Suborder: | Theropoda |
| Family: | †Ceratosauridae |
| Genus: |
†Ceratosaurus Marsh, 1884 |
| Species | |
| Synonyms | |
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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 followed the bauplan typical for large theropod dinosaurs. A biped, it moved on powerful hind legs, while its arms were reduced in size. The holotype specimen was an individual about 5.3 metres (17 ft) long; it is not clear whether this animal was fully grown. Marsh (1884) suggested that the holotype individual weighed about half as much as Allosaurus. In more recent accounts, it was estimated at 418 kilograms (922 lb), 524 kilograms (1,155 lb) and 670 kilograms (1,480 lb) by separate authors. Two skeletons, assigned to the new species C. magnicornis and C. dentisulcatus by James H. Madsen and Samuel P. Welles in a 2000 monograph, were substantially larger then the holotype. The larger of these, C. dentisuclatus, was informally estimated by Madsen to have been around 8.8 metres (29 ft) long. American science writer Gregory S. Paul, in 1988, estimated the C. dentisulcatus specimen at 980 kilograms (2,160 lb). A considerably lower figure, 275 kilograms (606 lb) for C. magnicornis and 452 kilograms (996 lb) for C. dentisulcatus, was proposed by John Foster in 2007.
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