Ceratosaurus nasicornis (S/F) / (S/F-JWE)

Ceratosaurus, meaning “horned reptile” for the distinctive horn on its snout, was a species of small to medium-sized ceratosaurid theropod. It lived during the late Jurassic period from about 153 to 148 million years ago; the type species, C. nasicornis, is known only from North America, but fragmentary remains of other possible species have been found in Europe. Both parts of its binomial name refer to its horn; Ceratosaurus, of course, means “horned reptile,” while nasicornis means “nose horn.”

Ceratosaurus belongs to the infraorder Ceratosauria and to the family Ceratosauridae, both of which are named after the animal. The first specimen was found by farmer Marshall Parker Felch in 1883, and he excavated it over the course of the next year. Most of the skeleton was complete, including the skull. The fossil was discovered in Garden Park just outside of Canon City (now Cañon City), Colorado; it was shipped to the Peabody Museum of Natural History where it was examined and named by paleontologist Othniel Charles Marsh in 1884. At the time, it was the most complete theropod fossil discovered in the United States of America.

More Ceratosaurus remains would not be found until the 1960s. A specimen unearthed in Utah’s Cleveland-Lloyd Dinosaur Quarry proved to be among the largest of its kind; a sub-adult was eventually found near Fruita, Colorado in 1976 by Thor Erikson. In 2000, paleontologists suggested that the large specimen from Utah should belong to a new species C. dentisculatus while the smaller specimen from Colorado should likewise be classified as C. magnicornis. Not all modern paleontologists agree, suggesting instead that these two represent growth stages and not distinct species.

Some remains found outside of North America have also been attributed to Ceratosaurus. Some have been found in the Tendaguru Formation in Tanzania, and bones which may belong to this dinosaur have also been found in the Lourinhã Formation of Portugal. A single tooth found near Moutier, Switzerland may belong to Ceratosaurus as well.

At the end of the 20th century, International Genetic Technologies successfully cloned Ceratosaurus nasicornis on Isla Sorna. During this time, heavy restrictions on genetic engineering were in place through the Gene Guard Act, so the creation of this animal was in violation of the law. It is not known how much control Simon Masrani or Henry Wu had over this activity, or to what degree they were even aware of it. Due to improper management on the part of InGen, this dinosaur is believed to have become extinct.


Ceratosaurus was a medium-sized carnivorous theropod, easily distinguished by its vivid coloration and prominent nasal horn. Adults reached lengths of 30.5 feet and grow to be 12 feet tall, noticeably larger than currently-known fossil specimens (which reach lengths of 18.7 feet or 5.69 meters). They may have weighed up to one ton. The skull is large for its body size, and its jaws are lined with a row of long blade-like teeth. When its mouth is closed, most of these teeth are hidden, but ten or more teeth in the the upper jaw protrude out of the mouth.

The nasal horn is ridge-like and shaped like an equilateral triangle. It is not very sharp, and is roughly a foot tall in adults; it is much thinner from side to side, located on the midline of the snout. The skull of the animal also has small hornlets above its eyes, and small conical osteoderms on its crown. More elongated osteoderms continue in a row down the midline of the animal’s thick neck and all the way down its back to its tail, located above the neural spines. This feature is unique among theropods known in the fossil record. Its eyes are relatively small, with yellow-orange sclerae and circular black pupils. The nostrils are somewhat large, likely giving it a good sense of smell.

Detail on the face of an adult Ceratosaurus. Note that ten teeth of the upper jaw remain exposed when the mouth is shut.

The body is overall fairly robust, with a thick neck and stocky chest. Even the tail is thick, tapering down to a small point. The arms are small, with four minute fingers on each hand; the legs are thicker and stronger, with three clawed toes on each foot. Its tail is deep from top to bottom, somewhat like a crocodile’s. Its body is more compact than fleet-footed theropods such as Allosaurus, with shorter legs and a low-built torso.

Coloration of the Ceratosaurus is, perhaps, one of its most striking features. The head is a vibrant shade of red, with some whitish stripes along the upper lips and slightly darker scales around the eyes. Starting around the neck and going all the way to the tail are gray or black irregular stripes, overlaying the animal’s base coloration. These are most vibrant on the neck, becoming gradually more faded toward the tail; they do not extend to the underbelly. The red coloration of the head also fades over the rest of the body, being replaced with a pale yellow color; its underbelly is even lighter, being almost white. On the tail, the gray stripes come closer together, eventually occupying more space than the light yellow base color.

Concept art by Shaun Keenan depicting a baby Ceratosaurus (top) alongside a Yutyrannus and Cryolophosaurus.

The hatchling stage has only been depicted in concept art. Like many baby animals, it has a proportionally large head, with its body being smaller by comparison. It lacks the distinctive coloration of the adult, and its nasal horn and osteoderms are less prominent at this stage. The teeth are smaller and less exposed.

One individual hatched in 1998 or 1999 had reached adulthood by 2001, meaning it grew from infancy to adulthood in two or three years. This was presumably achieved by the use of growth-enhancing supplements provided by Masrani Global Corporation personnel.

Sexual Dimorphism

Some Ceratosaurus are much duller in color than others, appearing mostly gray without the vibrant red and yellow markings, and only faded stripes. These less colorful animals are assumed to be the females, while the brightly-hued individuals are assumed to be male.

Preferred Habitat

This species has been sighted in heavily forested area and is generally seen near sources of water, where it drinks and finds its food. In the Jurassic period, this animal would have inhabited wetlands, lakes, and floodplains.

Jurassic World: Evolution portrays it as preferring 17,700 square meters of grassland with 4,400 square meters of forest within its territory.

Isla Nublar

In late 2004, all surviving Ceratosaurus were transported from Isla Sorna to Isla Nublar. After a few weeks in a quarantine pen, each animal would be introduced to a habitat, presumably in Sector 5 away from the park proper. There were at least three Ceratosaurus living on the island as of 2015: two gray individuals assumed to be females, and one more brightly-colored animal assumed to be a male. They were sighted in the vicinity of Camp Cretaceous between January 13 and January 14. There is no evidence that this animal was ever intended for exhibition in the park.

A report released by the Dinosaur Protection Group on February 4, 2018 implied that Ceratosaurus had gone extinct on Isla Nublar.

Isla Sorna

Sometime between late 1998 and mid-1999, Ceratosaurus was cloned on Isla Sorna by InGen under its new parent company Masrani Global Corporation. These animals were created in violation of the Gene Guard Act. Within nine months of their creation, they were abandoned to roam the island.

On the night of July 19, 2001, one adult Ceratosaurus was seen on the western bank of Isla Sorna’s central channel. Because of its bright colors, it is assumed to have been a male. It is not known how many animals, if there were more than one, existed on the island.

Known range of C. nasicornis on Isla Sorna as of July 19, 2001

The interference on Isla Sorna by Masrani Global Corporation caused an ecological collapse over the next five years, and in late 2004, any surviving Ceratosaurus would have been collected and transported to Isla Nublar.


Dinosaur poaching in the Muertes Archipelago and near Isla Nublar was a problem between 1997 and 2018. As there is currently no list of species that are believed to have been poached, it is unknown if Ceratosaurus was among them.

Behavior and Ecology
Daily Activity

Ceratosaurus is mainly active at night, coming out to hunt under cover of darkness. However, it is not nocturnal; during the daytime it patrols its territory, drinks, and bathes. This activity classifies it as cathermal.

Diet and Feeding Behavior

This dinosaur is carnivorous and hunts live prey. Its blade-like teeth are capable of inflicting injury to prey, but as the teeth in the very front of the mouth are the largest, it is less able to tear into larger prey items with its entire mouth. Instead, it probably delivers wounding bites and wait for its prey to weaken. Smaller prey is more easily killed, so it can probably make just one bite to take out a human-sized animal.

Based on fossil evidence, Ceratosaurus is believed to have lived near bodies of water and may have been a skilled swimmer. This would allow it to prey on fish, turtles, and other aquatic life. On Isla Sorna, the river where this dinosaur was sighted was home to fish such as bonitos. The mobile game Jurassic Park: Builder describes this animal as being an excellent swimmer which feeds on fish and marine reptiles, suggesting that it may have ventured into shallow oceanic environments to search for food.

Video games have consistently portrayed it as feeding primarily on small to medium animals and carrion, as well as displaying cannibalistic tendencies in Jurassic Park: Operation Genesis. This game identifies the Ceratosaurus as being a generalist feeder, not being picky about its diet (though the game states that its favored prey is Dryosaurus, a species which was not cloned in the films). They are portrayed in the game as being capable of hunting in groups, but also solitary hunting. It is portrayed in Jurassic World: Evolution as having a large appetite for its size.

According to the Jurassic World Facts mobile application, Ceratosaurus is not a powerful biter, but can run relatively fast. This suggests that it tires out terrestrial prey through chasing rather than ambushing with a strong biting attack.

Social Behavior

These dinosaurs are usually solitary, preferring to travel alone. They mostly congregate near sources of water.

Its physical features indicate that it does engage in some degree of social interaction, as its striking pattern would make it poor at camouflaging and its nasal horn is not robust enough to serve any combative purpose. The mobile application Jurassic World Facts states that the horn, at least, serves as a display structure during courtship, but also states that this species is a lone hunter.

The game Jurassic Park: Operation Genesis portrayed the animal as comfortable in small to medium groups, but without strong social instincts and a tendency toward cannibalism. Groups are portrayed hunting together when prey is available. This game’s spiritual sequel, Jurassic World: Evolution, portrayed the animal as being less social; it becomes stressed in groups of more than three, and as in the original game, it rarely socializes with others of its kind.


As a dinosaur, this animal would have laid eggs to reproduce. However, specific details about its reproductive behaviors are unknown. Its nasal horn, bright facial coloration, and elongated spinal osteoderms all indicate that it would have engaged in some kind of display behavior, but the nature of such behaviors are unknown. Other theropods are portrayed as having cloacae in Jurassic Park: The Game, but details about the reproductive anatomy of Ceratosaurus have not been disclosed.

Jurassic World Facts states that the horn plays a role in courtship displays, but does not go into detail on how it is used.

Theropod eggs are ovoid, like those of birds. This evolutionary trait discourages them from rolling away from where the parents place them. Ceratosaurus was a medium-sized theropod, so its eggs likely incubated for around six months before hatching.


Ceratosaurus has been heard to make low growling or gurgling noises when alone, and was heard making a groaning sound when frightened. Its nasal horn and bright colors are believed to have social functions, since they would not help it in other ways.

The video game Jurassic World: Evolution gives it a range of loud roars which it uses to confront rivals and establish territory.

Ecological Interactions
Ceratosaurus displaying a fear response

This animal was known to share some overlapping territory on Isla Sorna with the much larger Spinosaurus. On one occasion, a Ceratosaurus was seen smelling dung from a Spinosaurus and immediately retreating from the area, suggesting an antagonistic relationship between this animal and its larger, stronger, and more aggressive neighbor.

Though a predator, it can coexist relatively peacefully alongside many other dinosaur species. A few were known on Isla Nublar to frequent watering holes alongside herbivores such as Stegosaurus, SinoceratopsParasaurolophus, Brachiosaurus, and Ankylosaurus. Many of these well-armored and large dinosaurs would present a challenge for any hunter, and since it preys mainly on aquatic life, the Ceratosaurus likely poses them little threat. Carnivores known from the area were Pteranodon, Tyrannosaurus, Velociraptor, Baryonyx, and Compsognathus; however, aside from the tiny compies, Ceratosaurus was not observed alongside these animals. This implies that it avoids watering holes when potential rivals or threats are there.

As with nearly all de-extinct species, InGen’s ability to extract its DNA would be reliant on the fact that hematophagous, or blood-drinking, parasites such as female mosquitoes fed upon the blood of this animal. It is not known whether hematophagous species from the modern day still used it as a host.

The video game Jurassic World: Evolution portrays it as preferring a solitary life with few other species nearby. It is a host to the bacterium Campylobacter, which can sometimes cause the animal to become sick with campylobacteriosis. This bacterium is common in modern birds, inhabiting up to 100% of some poultry in real life.

Relationship to Humans

Ceratosaurus is, perhaps, one of the least aggressive and most docile carnivorous dinosaurs. The first confirmed encounter was in 2001, in which a Ceratosaurus investigated a small group including Dr. Alan Grant, Paul Kirby, and Amanda Kirby. The animal showed no signs of aggression, sniffed them, and retreated into the forest upon smelling Spinosaurus dung on them. It has been suggested that it was discouraged from eating them by the smell, but during the encounter it did not make any attempt to attack; instead, the animal simply appeared to be curious.

Its existence was of concern to Masrani Global Corporation, as it was not on InGen’s species list and therefore was substantial evidence that InGen had violated the Gene Guard Act. The survivors of the incident on Isla Sorna in 2001 were silenced from speaking about this animal’s existence following their rescue. Specimens were relocated to Isla Nublar in 2004, where they were ostensibly held as future attractions; however, it is not known whether they were ever exhibited in the park. They are absent from the official Jurassic World website, along with other animals which were known to be on the island but not on exhibition. Therefore, it is most likely that Ceratosaurus was never placed in a park attraction.

Along with three other genera of dinosaur, Ceratosaurus was used as evidence during the 2016 investigation by the United States Congress into violation of the Gene Guard Act by InGen. An anonymous hacker revealed in late 2015 during the inquiry into Jurassic World that these four dinosaur genera were created illegally between 1998 and 1999, and three months later, the US Congress announced that it was open to inquiry into violation of the Gene Guard Act.

Like all animals, though, it is not to be treated as harmless, especially if it is encountered at night. Humans are not its normal prey, but if it finds a person while hunting, it will not turn down a meal and may give chase. The best way to drive it off is with sudden flashes of light, as these will startle and temporarily blind it. If it becomes disoriented, it will give up the chase. Another way to escape it is to rely on the presence of larger and more dominant predators, but this is inadvisable as it requires one being near other dangerous animals.

Based on Jurassic World: Evolution, the cost for raising a Ceratosaurus from fertilization to maturity as of 2018 would be $550,000.

Behind the Scenes

It was originally thought that the CGI model of the Ceratosaurus resembled that of the Tyrannosaurus, and as a result the Ceratosaurus was speculated to be a mutant by some members of the Jurassic fandom. Such fans, including some progenitors to this Encyclopedia project, classified this animal as Ceratosaurus “mutatus” (x Tyrannosaurus rex); it was suggested that InGen may have filled in the gaps in the Ceratosaurus genome with tyrannosaur DNA. However, this was entirely speculative and is considered inaccurate now, as the Ceratosaurus from the Jurassic Park /// dinosaur charts demonstrate otherwise. We therefore believe that the animal in the film can indeed be classified as Ceratosaurus nasicornis.

In the original script for the film, the characters would have encountered a Carnotaurus during this scene instead. Unlike the Ceratosaurus, this animal acted aggressively toward the humans and was only repelled by the smell of spinosaur dung.

Disambiguation Links

Ceratosaurus nasicornis (IDW-JPR)