Ceratosaurus/ˌsɛrətoʊˈsɔːrəs/ (from Greek κέρας/κέρατος, keras/keratos meaning "horn" and σαῦρος sauros meaning "lizard") was a carnivorous theropod dinosaur that lived in the Late Jurassic period (Kimmeridgian to Tithonian ages). The genus was first described in 1884 by American paleontologist Othniel Charles Marsh based on a nearly complete skeleton discovered in Garden Park, Colorado, in rocks belonging to the Morrison Formation. The type species is Ceratosaurus nasicornis.
The Garden Park specimen remains the most complete skeleton known from the genus and only a handful of additional specimens have been described since. Two additional species, Ceratosaurus dentisulcatus and Ceratosaurus magnicornis, were described in 2000 from two fragmentary skeletons from the Cleveland-Lloyd Quarry of Utah and from the vicinity of Fruita, Colorado. The validity of these additional species has been questioned, however, and all three skeletons possibly represent different growth stages of the same species. In 1999, the discovery of the first juvenile specimen was reported. In 2000, a partial specimen was excavated and described from the Lourinhã Formation of Portugal, providing evidence for the presence of the genus outside of North America. Fragmentary remains have also been reported from Tanzania, Uruguay, and Switzerland, although their assignment to Ceratosaurus is currently not accepted by most paleontologists.
Ceratosaurus was a medium-sized theropod. The original specimen is estimated to be 5.3 m (17 ft) or 5.69 m (18.7 ft) long, while the specimen described as C. dentisulcatus was larger, at around 7 m (23 ft) long. Ceratosaurus was characterized by deep jaws that supported proportionally very long, blade-like teeth, a prominent, ridge-like horn on the midline of the snout, and a pair of horns over the eyes. The forelimbs were very short, but remained fully functional. The hand had four fingers with claws on the first three. The tail was deep from top to bottom. A row of small osteoderms (skin bones) was present down the middle of the neck, back, and tail. Additional osteoderms were present at unknown positions on the animal's body.
Ceratosaurus gives its name to Ceratosauria, a clade of theropod dinosaurs that diverged early on from the evolutionary lineage leading to modern birds. Within Ceratosauria, some paleontologists proposed it to be most closely related to Genyodectes from Argentina, which shares the strongly elongated teeth. The geologically older genus Proceratosaurus from England, although originally described as a presumed antecedent of Ceratosaurus, was later found to be an early tyrannosauroid. Ceratosaurus shared its habitat with other large theropod genera, including Torvosaurus and Allosaurus, and it has been suggested that these theropods occupied different ecological niches to reduce competition. Ceratosaurus may have preyed upon plant-eating dinosaurs, although some paleontologists suggested that it hunted aquatic prey such as fish. The nasal horn was probably not used as a weapon as was originally suggested by Marsh, but more likely was used solely for display.
specimens have been described since. Two additional species, Ceratosaurus dentisulcatus and Ceratosaurus magnicornis, were described in 2000 from two fragmentary...
family's type genus, Ceratosaurus, was first found in Jurassic rocks from North America. Ceratosauridae is made up of the genera Ceratosaurus, found in North...
type species, Ceratosaurus nasicornis, described by O.C. Marsh in 1884. A moderately large predator from the Late Jurassic, Ceratosaurus nasicornis, was...
Jurassic of Switzerland. However, a recent overview of Ceratosaurus included it in Ceratosaurus sp. Apatodon mirus, based on a scrap of vertebra Marsh...
of Ceratosaurus, due to the partially preserved portion of the crest of Proceratosaurus superficially resembling the small crest of Ceratosaurus. Now...
large theropods such as Allosaurus, Ceratosaurus, and Saurophaganax in the United States, Allosaurus, Ceratosaurus, and Lourinhanosaurus in Portugal, possibly...
and terrorize Los Angeles. These prehistoric animals include a giant Ceratosaurus, raptorlike Carnotaurus, building-climbing Spinosaurus, and brutal Pteranodon...
significantly reduced form. The somewhat more advanced ceratosaurs (including Ceratosaurus and Carnotaurus) appeared during the Early Jurassic and continued through...
Genyodectes was closer to Ceratosaurus than the more derived abelisaurs (that also descended from animals like Ceratosaurus). Also, by studying historical...
portrayals of cavemen and dinosaurs together, with its depiction of a Ceratosaurus. The film reinforced the incorrect notion that non-avian dinosaurs co-existed...
"Crash" Corrigan as The Sloth / Ceratosaurus Snub Pollard as a Singapore Barfly Harry Wilson as Barfly Ceratosaurus Brontosaurus Megatherium Dimetrodon...
Torvosaurus, a large Jurassic carnivore, from North America and Europe Ceratosaurus, a medium-sized Jurassic carnivore from North America, Europe, and possibly...
Predators in this paleoenvironment included the theropods Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes, and Allosaurus, which accounted...
defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely...
Nanosaurus; as well as the carnivorous theropods Allosaurus, Marshosaurus and Ceratosaurus. This formation was a hotspot of sauropod biodiversity, with over 16...
more closely related to Noasaurus than to Elaphrosaurus, Abelisaurus, Ceratosaurus, or Allosaurus". Masiakasaurus (and presumably other noasaurines) had...
it to portray the Mamenchisaurus, which was fully computer-generated. Ceratosaurus and Corythosaurus are introduced in Jurassic Park III, through brief...
great size may have been a deterrent to the predators Allosaurus and Ceratosaurus: their remains have been found in the same strata, which suggests that...
Jurassic, but no body remains are known until the Cretaceous. Skeleton of Ceratosaurus, a ceratosaurid from the Late Jurassic of North America Skeleton of Monolophosaurus...
remained relatively conservative, resembling those of the more basal Ceratosaurus. Both the pelvis and hind limb were long and slender. The left femur...
featured in earlier films included the Ankylosaurus, in addition to Ceratosaurus and Corythosaurus. Paleontologist Jack Horner worked as the film's technical...
Madsen along with Samuel Paul Welles published an osteology of two Ceratosaurus species they named, C. magnicornis & C. dentisulcatus, from Grand Junction...
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