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Ceratosaurus |
| Ceratosaurus Fossil range: Late Jurassic |
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 Ceratosaurus skeleton mount
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Ceratosaurus (pronounced /ˌsɛrətəˈsɔrəs/) meaning 'horned lizard', in reference to the horn on its nose (Greek κερας/κερατος, keras/keratos meaning 'horn' and σαυρος/sauros meaning 'lizard'), was a large predatory dinosaur from the Late Jurassic 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 (Sereno 1997) (i.e. similar to modern birds). A row of small osteoderms was present down the middle of the back.1
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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 were described in 2000,2 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:
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.1 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.3 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.
Relatives of Ceratosaurus include Genyodectes, Elaphrosaurus, and the abelisaur Carnotaurus. The classification of Ceratosaurus and its immediate relatives has been under intense debate recently. Ceratosaurus is unique in its characters; it is too advanced and basal 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 than Allosaurus. As with all dinosaurs, the more fossils found of these animals, the better their evolution and relationships can be understood.
Ceratosaurus has appeared in several films, including the first live action film to feature dinosaurs, D. W. Griffith's Brute Force (1914).4 In the Rite of Spring segment of Fantasia (1940), Ceratosaurus are shown as opportunistic predators attacking Stegosaurus and Diplodocus trapped in mud. 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.
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 (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 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.
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