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Ceratosaurus

'''''Ceratosaurus''''' () meaning 'horned lizard', in reference to the horn on its nose (Ancient Greek|Greek ''κερας/κερατος, keras/keratos'' meaning 'horn' and ''σαυρος''/''sauros'' meaning 'lizard'), was a large predatory dinosaur from the Late Jurassic Period (geology)|Period, found in the Morrison Formation of North America, in Tanzania and Portugal. It was characterized by large jaws with blade-like teeth, a large, blade-like horn on the snout and a pair 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 (Paul Sereno|Sereno 1997) (i.e. similar to modern birds). A row of small Armour (zoology)|osteoderms was present down the middle of the back.Gilmore CW. 1920, Osteology of the Carnivorous Dinosauria in the United States National Museum. United States National Museum Bulletin. 110, pages 1-154

Discovery and species

Ceratosaurus is known from the Cleveland Lloyd Dinosaur Quarry in central Utah and the Dry Mesa Quarry in Colorado. The type species, described by Othniel Charles Marsh|O. C. Marsh in 1884 and redescribed by Gilmore in 1920, is ''Ceratosaurus nasicornis''. Two further species were described in 2000, Madsen JH, Welles SP. Ceratosaurus (Dinosauria, Therapoda), a Revised Osteology. Miscellaneous Publication. Utah Geological Survey. ISBN 1-55791-380-3 ''C. magnicornis'', and ''dentisulcatus''. ''C. magnicornis'' has a slightly rounder horn but is otherwise highly similar to ''C. nasicornis''; ''C. dentisulatus'' is larger (over 7 meters), slightly more derived, and has an unknown horn shape (assuming it had them). The Portuguese remains have recently been ascribed to ''C. dentisulcatus'' (Mateus et al 2006). More additional species, including ''C. ingens'' and ''C. stechowi'', have been described from less complete material. If ''C. ingens'' is valid, then at least one species of ''Ceratosaurus'' was as large as ''Torvosaurus'' and ''Epanterias'' that lived alongside it. Ceratosaurus species:
- ''C. nasicornis'' (type species|type)
- ''C. dentisulcatus''
- ''C. magnicornis''
- ''C. ingens
- ''C. stechowi
- ''C. meriani

Paleobiology

Ceratosaurus lived alongside dinosaurs such as ''Allosaurus'', ''Torvosaurus'', ''Apatosaurus'', ''Diplodocus'', and ''Stegosaurus''. It may have competed with ''Allosaurus'' for prey, though it was smaller at around 6 to 8 meters (20-27 feet) in length, 2.5 meters (8 feet) tall, and weighing 500 kg up to 1 tonne; it would have occupied a distinctly separate niche from its larger cousin which is estimated to have grown up to 12 metres in length with the largest definitive specimen of 9 metres. ''Ceratosaurus'' had a longer, more flexible body, with a deep tail shaped like that of a crocodilian. This suggests that it was a better swimmer than the stiffer ''Allosaurus''. A recent study by Bakker suggested that ''Ceratosaurus'' generally hunted aquatic prey, such as fish and crocodiles, although it had potential for feeding on large dinosaurs. The study also suggests that sometimes adults and juveniles ate together. This evidence is debatable, and ''Ceratosaurus'' tooth marks are very common on large, terrestrial dinosaur prey fossils. Scavenging from corpses, smaller predators, and after larger ones also likely accounted for some of its diet.

Classification

Relatives of ''Ceratosaurus'' include ''Genyodectes'', ''Elaphrosaurus'', and the abelisaur ''Carnotaurus''. The Taxonomic classification|classification of ''Ceratosaurus'' and its immediate relatives has been under intense debate recently. ''Ceratosaurus'' is unique in its synapomorphy|characters; it is too advanced and Basal (phylogenetics)|basal tetanurae|tetanuran-like to be a large, late coelophysoid; and too primitive in many manners to be a true carnosaur. Its closest relatives appear to be the abelisaurs from the Cretaceous, but again, ''Ceratosaurus'' is an enigma in its existing tens of millions of years before them with no obvious Early Cretaceous link between them. In the past, ''Ceratosaurus'', the Cretaceous abelisaurs, and the primitive coelophysoids were all grouped together and called Ceratosauria, defined as "theropods closer to ''Ceratosaurus'' than to Aves". Recent evidence, however, has shown large distinctions between the later, larger and more advanced ceratosaurs and earlier forms like ''Coelophysis''. While considered distant from birds among the theropods, ''Ceratosaurus'' and its kin were still very bird-like, and even had a more avian Tarsus (skeleton)|tarsus (ankle joint) than ''Allosaurus''. As with all dinosaurs, the more fossils found of these animals, the better their evolution and relationships can be understood.

In popular culture

Ceratosaurus has appeared in several films, including the first live action film to feature dinosaurs, D. W. Griffith's ''Brute Force'' (1914). In the The Rite of Spring|Rite of Spring segment of ''Fantasia (film)|Fantasia'' (1940), ''Ceratosaurus'' are shown as opportunistic predators attacking ''Stegosaurus'' and ''Diplodocus'' trapped in mud. In ''The Animal World (film)|The Animal World'' (1956) a ''Ceratosaurus'' kills a ''Stegosaurus'' in battle, but is soon attacked by another ''Ceratosaurus'' trying to steal a meal. This scene ends with both ''Ceratosaurus'' falling to their deaths off the edge of a very high cliff. A ''Ceratosaurus'' battles a ''Triceratops'' in the 1966 remake of ''One Million Years B.C.''. ''Ceratosaurus'' is also featured in ''The Land That Time Forgot (film)|The Land That Time Forgot'' (1975) where it battles a ''Triceratops'', and its sequel ''The People That Time Forgot (film)|The People That Time Forgot'' (1977) in which Patrick Wayne's character rescues a cavegirl from two pursuing ''Ceratosaurus'' by driving the dinosaurs off with smoke bombs (after having failed to frighten them off by firing shots in the air once the ''Ceratosaurus''' attention had been shifted to Patrick Wayne's party of explorers). More recently, a ''Ceratosaurus'' makes a brief appearance in the film ''Jurassic Park III'' in which it is repelled from attacking the main characters by a large mound of ''Spinosaurus'' dung. This dinosaur also appears in the television documentary ''When Dinosaurs Roamed America'', a ''Ceratosaurus'' makes a few appearances as a predator, killing ''Dryosaurus'' and eating it, but is later killed and eaten by an ''Allosaurus''.Ceratosaurus is also featured in episodes of ''Jurassic Fight Club'' where it is seen as a rival to ''Allosaurus'' and preying on ''Stegosaurus''. >

References

- Mateus, O., Walen, A. & Antunes, M.T. (2006). The large theropod fauna of the Lourinhã Formation (Portugal) and its similarity to the Morrison Formation, with a description of a new species of Allosaurus. in Foster, J.R. and Lucas, S. G. R.M., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36

Footnotes

Category:Ceratosaurs Category:Jurassic dinosaurs Category:Dinosaurs of Africa Category:Dinosaurs of Europe Category:Dinosaurs of North America simple:Ceratosaurus

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