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Ceratosaurus nasicornis Dinosaur Facts

Ceratosaurus inhabited the floodplains and riverine forests of North America at the same time as the theropod predator Allosaurus and the sauropods Brachiosaurus and Apatosaurus. Ceratosaurus, however, was more primitive than its Upper Jurassic counterpart because it retained the anatomical remains of its ancestors (a clawed fourth finger unlike other theropods that usually have only three) and its population was much more restricted, much to the delight of herbivores of the region, as evidenced by the very few fossils discovered compared to those of Allosaurus that abound in the Morrison Formation.

Long teeth

Ceratosaurus teeth

Being both medium-sized theropods tracking the Utah and Colorado regions 150 million years ago, it's a safe bet that these creatures would occasionally compete for the same food sources. Ceratosaurus and Allosaurus had a powerful jaw that was designed to slice and chop. Because a similar bite often means a similar diet, maybe these two titans hunted the same game. On the other hand, Allosaurus had proportionally smaller teeth while those of Ceratosaurus were very long; the upper dentition of a specimen in particular is so elongated that when it has the jaw completely closed it extends further than the lower jaw.

Ceratosaurs theropods

In addition to dental differences, the head of Ceratosaurus is easily recognized by its distinctive features: a small protruding nasal horn, small bumps above the eyes and a row of bony plates called osteoderm that stretched along its spine. For these reasons, it is generally classified in its own infra-order, the ceratosaurians, and the dinosaurs which resemble it strangely are called ceratosaurs. These dinosaurs were in fact quite distant from other theropods such as Tyrannosaurus and Allosaurus and probably more related to coelophysids and abelisaurids, a Cretaceous group living in the southern hemisphere.

Movie star

Very few people are aware, but Ceratosaurus has been a movie celebrity for over 100 years. The audience watched him track down Cro-Magnon men in Brute Force (1914), tackle a Triceratops in One Million Years BC (1966) and have fun at the sight of Spinosaurus droppings in Jurassic Park III (2001). All these cameos have greatly contributed to improve its popularity.

Ceratosaurus vs Triceratops in 1 Millions Years BC

Possibly semi-aquatic

Osteoderms of Ceratosaurus are not the only characteristic that the latter has in common with modern alligators. Like the alligators, the tail of Ceratosaurus was broad, powerful and flexible indicating that this dinosaur was possibly a semi-aquatic animal. Ceratosaurus teeth are sometimes found scattered near lung-fish skeletons. According to paleontologist Robert Bakker, the idea that this dinosaur may have been amphibian is plausible. He even considers the Ceratosaurus as a kind of crocodile to become, stealthily poking under the rivers of the Jurassic. For many people, Baker's visions are completely far-fetched and considered pure speculation. Until now, the only dinosaur considered officially semi-aquatic is the gigantic African theropod Spinosaurus whose proof of its ability to swim are much more convincing.

Nasal horn

Ceratosaurus skull

One of the most misunderstood features of Ceratosaurus skull is its nasal horn, which looked rather like a rounded hump and was in no way comparable to the slender horns of a creature like the Triceratops. The famous American paleontologist Othniel C. Marsh, who named the dinosaur "horned lizard" on the premise of vestiges discovered in Colorado and Utah, considered the horn as an offensive weapon, but the most likely explanation is that this bony protuberance was a feature of sexual selection - a more prominent horn was more attractive to females.


Ceratosaurus fossil

The earliest fossils of Ceratosaurus were unearthed in Cleveland-Lloyd's dinosaur quarry and in Colorado's Dry Mesa quarry. These two fossil quarries are part of the Morrison Formation, Upper Jurassic-era sedimentary rocks centered in Wyoming and extending over a vast area of the western United States. Although this dinosaur is frequently cited as being purely North American, Ceratosaurus skeleton have also been found in Portugal and Tanzania.


To date, there are five species of this dinosaur, the best known of which is C. nasicornis which ranked among the medium sized theropods with a length of about 20 feet for a weight of 1 ton. Reaching more than 23 feet from head to tail, C. dentisculatus was visibly longer than C. nasicornis and probably twice as massive.

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