Ceratosaurus sketch2
Conservation status
Extinct (fossil)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Infraorder: Ceratosauria
Family: Ceratosauridae
Genus: Ceratosaurus
Marsh, 1884
  • C. nasicornis (type)
  • C. dentisulcatus
  • C. magnicornis
  • C. ingens

Ceratosaurus meaning 'horned lizard', in reference to the horn on its nose (Greek keras/keratos meaning 'horn' and sauros meaning 'lizard'), was a large predatory dinosaur from the Late Jurassic Period, found in the Morrison Formation of North America, in Tanzania and possibly in Portugal. It was characterized by large jaws with enormous, bladelike 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 (Sereno 1997) (i.e. similar to modern birds). Evidence suggests that there may also have been a row of small spurs or even a low sail, along the spine.

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 O. C. Marsh in 1884 and redescribed by Gilmore in 1920, is Ceratosaurus nasicornis. Two further species have recently been described in 2000[1], C. magnicornis, and dentisulcatus. However, additional species, including C. ingens, C. stechowi and a species that has been referred to as C. meriani, from Portugal, have been described from less complete material. C. nasicornis, the type species, is cited at around 6 meters (20 feet) in length.

Ceratosaurus species

  • C. nasicornis (type)
  • C. dentisulcatus
  • C. magnicornis
  • C. ingens


Ceratosaurus size comparison

Relative sizes of humans and Ceratosaurus.

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, weighing 500 kg up to 1 tonne. Ceratosaurus had a longer, more flexible body, with a tail shaped like a crocodilian [2]. This suggests that it was a better swimmer than the stiffer Allosaurus. A recent study by Bakker[3] confirmed that Ceratosaurs 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, of course, very debatable and Ceratosaurus tooth marks are very common on large, terrestrial dinosaur prey fossils.


Relatives of Ceratosaurus include Elaphrosaurus and the abelisaur Carnotaurus. The classification of Ceratosaurus and its immediate relatives has been under intense debate recently. In the past, Ceratosaurus, the Cretaceous Albelisaurs and the primitive Coelophysoidae were all grouped together and called Ceratosauria, defined as theropods closer to Ceratosaurus than to the lineage of aves. Recent evidence, however, has shown large distinctions between the later, larger and more advanced Ceratosaurs and earlier forms like Coelophysis, leading to the naming of the later theropods as Neoceratosauria and closer to, or perhaps even ancesteral to, Tetanuran carnosaurus like Allosaurus. Many Theropods no longer considered close to Ceratosaurus were once classified as relatives, including Eustreptospondylus and Yangchuanosaurus. While it is likely that they are not Neoceratosaurs these 'more advanced' theropods do display a sort of middle ground of primitive characteristics compared to Allosaurs (Eustreptospondylus lacks the Allosaur expanded boot-shaped pubic bone, instead having a rod shaped pubis like Ceratosaurus. Many Sinraptors and Allosaurs have a tendency to grow elaborate and multiple horn rows, very visible in Yangchuanosaurus and prominent in Ceratosaurus). Some of the most modern publishings have even begun listing Ceratosaurus as a basal Tetanurae and closer to Allosaurus than Coelophysis. While considered distant from the lineage of aves among the theropods, Ceratosaurus and its kin were still very bird-like and even had a more 'advanced-looking tarsus than Allosaurus. As with all dinosaurs, the more fossils found of these animals, the better their evolution and relationships can be understood.


An outdated reconstruction of Ceratosaurus

In popular culture

  • A Ceratosaurus battles a Triceratops in the 1966 remake of One Million Years B.C..
  • In Jurassic Park III, a Ceratosaurus has a brief appearance.
  • In the film When Dinosaurs Roamed America, a Ceratosaurus makes a few appearances but is later killed by an Allosaurus and eaten.
  • The famous Korean manhwa character Baby-Saurus Dooly, is known to be Ceratosaurus.
  • In 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.
  • Ceratosaurus is also featured in The Land That Time Forgot (1975) where it battles a Triceratops, and its sequel The People That Time Forgot (1977) in which Patrick Wayne's character rescues a cavegirl from two persuing 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).
  • Ceratosaurus is also featured in the Vivendi Universal game, Jurassic Park: Operation Genesis.


  1. Madsen JH, Welles SP. Ceratosaurus (Dinosauria, Therapoda), a Revised Osteology. Miscellaneous Publication. Utah Geological Survey. ISBN 1-55791-380-3
  2. Gilmore CW. 1920, Osteology of the Carnivorous Dinosauria in the United States National Museum. United States National Museum Bulletin. 110, pages 1-154
  3. Bakker RT, Bir G (2004). “Dinosaur Crime Scene Investigations”, Currie PJ, Koppelhus EB, Shugar MA, Wright JL: Feathered Dragons. Indiana University Press, 301–342. ISBN 0-253-34373-9..

Smallwikipedialogo.png This page uses content from Wikipedia. The original article was at Ceratosaurus. The list of authors can be seen in the page history. As with Paleontology Wiki, the text of Wikipedia is available under the GNU Free Documentation License.

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