Coelurus fragilis (S/F)

Coelurus, meaning “hollow tail,” is a species of small theropod dinosaur in the family Coeluridae. The type species, and only known species at this time, is Coelurus fragilis; the species name refers to the fragile nature of the animal’s fossilized remains. It lived during the late Jurassic period, 155 to 152 million years ago, in what is now Wyoming.

This species of dinosaur was described in 1879 by Othniel Charles Marsh, its fossils having been found at Como Bluff within the Morrison Formation. The fossil consists of vertebrae, bones of the arms and legs, and possibly a lower jaw fragment from a second individual. In the initial description, Marsh was chiefly impressed by the hollow vertebrae, from which he gave the dinosaur its genus name. Because the remains were so fragmentary, Marsh was not certain at first whether the creature was a dinosaur or some other type of reptile, but it was confidently found to be dinosaurian when he returned to study it again in the early 1880s.

Like many dinosaurs found during the Bone Wars, Coelurus has a long and confusing taxonomic history, and for many years it was used as a wastebasket taxon for all new coelurosaurians which looked similar to it. Species of Coelurus throughout history have been widely reassigned to other genera, such as CoelophysisOrnitholestes, and Tanycolagreus. Today, there is only one known species of Coelurus.

At some point between 2005 and 2015, Coelurus was cloned by International Genetic Technologies operating under the banner of Masrani Global Corporation. The dinosaur was recreated using ancient DNA recovered from Jurassic amber samples; it was intended for exhibition in the Jurassic World theme park, but there is currently no evidence that it was put on display. It is strongly suspected to have become extinct between late 2015 and 2017 due to neglect.


This is not a large dinosaur, reaching lengths of 7.9 feet (2.4 meters) and a height of 2.3 feet (70 centimeters) at the hips. Paleontologists estimate its weight to be 29 to 44 pounds (13 to 20 kilograms). The vertebrae of Coleurus, in addition to being hollow like a modern bird’s, are longer than average; this gives the animal a lengthened torso and very long tail. Its tail in particular is about half of its overall length.

Coelurus also has a long neck. Fossils of its skull have yet to be discovered, but depictions of the animal (from the Jurassic World Facts application and associated action figure, currently the only known modern depictions of Jurassic‘s Coelurus) show it to have a skull shape relatively similar to its relative Ornitholestes. The skull is perched atop the neck facing forward, with binocular vision and narrow jaws. Above its eyes are small, low triangular crests. According to the aforementioned application, the brain of Coelurus is twice as large as those of similarly-sized carnivorous animals.

The arms and legs of Coelurus are lanky. Its upper arm has a distinct S-shaped curve when viewed from the side and is slightly longer than the forearm, though in life the animal’s body may have obscured some of its upper arm length. Its thigh bones are S-shaped when viewed from the front, and its metatarsals are exceptionally long and slender. The hands and feet each have three digits ending in claws (each foot also has a fourth toe, a dewclaw, which is vestigial). According to the Jurassic World Facts application, Coelurus‘s long legs allow it to reach some of the fastest speeds of any theropod; for comparison, Velociraptor antirrhopus can reach speeds of fifty to sixty miles per hour when at a sprint.

Later theropods would possess cloacae, which would house their reproductive organs. It is most likely that an earlier theropod such as Coelurus already possessed this structure.

While fossils have yet to show whether this animal had feathers in prehistory, its de-extinct clones created by InGen are not believed to have any. Instead, its body is covered in scaly skin, with distinct raised scales on the back of the head and neck. It has been depicted as a brightly-colored animal, with a rosy red head; the color fades to pink on the neck and body, eventually becoming very pale and almost white on the tail. Its back has blue markings beginning just behind the eye orbits and extending to the hips. On the tail, this pattern changes to irregular stripes, ending almost at the halfway mark of the tail’s length. Its arms and lower legs are very pale pink, almost white, about the same color as the end of the tail. The underbelly is an off-white color as well, including the entire lower jaw.


No hatchlings or juveniles of Coelurus have yet been observed. Their growth patterns are unknown, though a smaller animal such as this may mature fairly fast. InGen is known to have used genetic and hormonal methods to accelerate the growth of their animals.

Sexual Dimorphism

There is currently no known sexual dimorphism in Coelurus. The animal depicted in the Jurassic World Facts application is said to be a female, and is the only known depiction of this creature in the franchise’s present day.

Preferred Habitat

Fossil evidence suggests that the Coelurus lived in semi-arid environments and is evolved to survive through wet and dry seasons. It inhabited floodplains, conifer forests, and savannas. In the modern day, it was able so survive in tropical environments with human assistance.

Muertes Archipelago

At the moment there is no evidence that this dinosaur was ever bred anywhere in the Muertes Archipelago. Its DNA had not yet been recovered by the time InGen abandoned its ventures on Isla Sorna, and activity on the island has been kept tightly under wraps in more recent times.

Isla Nublar

Sometime between 2005 and 2015, Coelurus was hatched on Isla Nublar with the intent to eventually exhibit it in the Jurassic World theme park. There is currently no evidence that any ever made it to display. They were likely housed in habitats in Sector 5, in the northern region of the island, though their population statistics for this time are unknown.

After the 2015 incident closed Jurassic World permanently, Coelurus and the other dinosaurs were able to roam the island and were left at the mercy of nature and each other. A report by the Dinosaur Protection Group released on February 4, 2018 heavily implies that Coelurus became extinct at some point before that date. No surviving populations have been confirmed.

Mantah Corp Island

Specimens and genetic samples of several InGen organisms were illegally appropriated by Mantah Corporation and held at a testing facility on their privately-owned island in the mid-2010s. It is unknown if Coelurus was among the species taken.

BioSyn Genetics Sanctuary

After the release of de-extinct animals into the Pacific Northwest in 2018, the task of rounding up more problematic animals and relocating them was opened to multiple governmental, international, and corporate entities. BioSyn was among the more prominent, having constructed the BioSyn Genetics Sanctuary in Italy in order to house de-extinct animals. However, Coelurus has not been listed among the species they possessed.

Black market

While no living specimens have been reported since before 2018, the DNA of this species presumably still exists in InGen’s genetic database. Many samples of DNA entered the black market in 2018 after de-extinction became open-source. If Coelurus has been bred, or if its genetic material is in circulation, it may possibly be found in the Amber Clave night market in Malta, which became a hub of de-extinction resource trade in the 2020s.

Wild populations

This dinosaur first evolved roughly 155 million years ago, during the Jurassic period, and existed for around three million years before going extinct. Like many prehistoric species, not enough is known about its range or biology to understand completely what caused it to become extinct, but environmental changes are the usual culprit. It existed in forested areas of western Laurasia, the area that became North America as the continent rifted apart. Fossilized remains contained enough DNA for scientists to clone the animal around 152 million years after it died out, using genetic engineering techniques to restore it to life in the early twenty-first century.

Isla Nublar and the Muertes Archipelago were subject to dinosaur poaching attempts throughout the 2000s and 2010s. It is currently unknown what species may have been illegally removed from the island, or where (aside from mainland Central America) they may have been taken. Coelurus, with its manageable size, could have easily been smuggled onto even smaller boats or aircraft. Unfortunately, there is no evidence that any are still living.

Behavior and Ecology
Activity Patterns

The activity patterns of Coelurus are presently unknown.

Diet and Feeding Behavior

Coelurus is a carnivore, feeding on smaller animals than itself. Its long arms and legs would help it to grapple with prey such as insects and small vertebrates, though it is likely not strong enough to threaten animals much larger than itself.

Social Behavior

If the bright colors of the Mattel Coelurus are taken as film canon, then Coelurus is most likely a social animal that uses visual displays.


All dinosaurs lay eggs to reproduce. Theropod eggs, like those of Coelurus, are typically ovoid in shape to prevent them from rolling. A small dinosaur like Coelurus would have an incubation period lasting around three to six months, though the actual incubation time is unknown due to a lack of observations.


Any vocalizations used by Coelurus are currently unknown. If it is brightly-colored as has been depicted, then it most likely uses forms of visual signalling.

Ecological Interactions

There is a lack of data on Coelurus ecology, but it is believed to have been a terrestrial hunter and fairly low on the food chain. Certainly, after being released into the wild of Isla Nublar, it would have been possible prey for a multitude of carnivorous de-extinct animals, which likely contributed to its decline on the island.

This animal likely fed on Isla Nublar’s smallest wildlife: lizards, frogs, rats, insects, and birds. It may have preyed upon the smallest of dinosaurs, including Compsognathus, Microceratus, and Segisaurus, while itself being prey to the larger theropods and other carnivores.

Cultural Significance

Coelurus is not a commonly depicted dinosaur species in art. It is sometimes used as an example of a generic small theropod of the Jurassic period.

In Captivity

This is one of the smaller de-extinct theropods and can probably be kept in captivity more easily than many of the bigger dinosaurs. It takes up less space and consumes less food than other species, making it cost-efficient. However, it is extremely speedy, making it potentially difficult to recapture if it escapes.

At the moment, nothing specific is known about this dinosaur’s needs in captivity, or how well it fared. However, it was never successfully integrated into Jurassic World despite being cloned before 2015, suggesting that there were difficulties in putting it on exhibit.


This dinosaur had a troubled paleontological history, having been uncovered during the Bone Wars and used as a wastebasket for many new theropod finds. Even modern phylogenetic studies do not always place Coelurus satisfactorily, finding its affinities uncertain. Scientists continue to debate exactly what manner of theropod this creature is.

Paleogenetics brought this species back to life on Isla Nublar, permitting a more in-depth scientific investigation. It is not known if InGen’s specimens were genetically pure enough to determine its exact taxonomic placement, but in any case, it probably provided useful research opportunities into theropod evolutionary biology. Sadly, nothing is yet known about InGen’s findings.


Being involved in the Bone Wars made this dinosaur political on a personal level, as well as within the scientific community, due to its contested classification. Numerous species were assigned to Coelurus historically and have since been reclassified. It would become subject to even more serious political debate after the 2015 incident on Isla Nublar, which cast it into the wild of the island and threatened its survival. Volcanic activity on the island increased the debate as the destruction of Isla Nublar’s ecosystem became imminent, and Coelurus was among the creatures whose existence was a part of the discussion.

While animal rights activists and other political groups debated the fate of Isla Nublar, Coelurus may have already become extinct by the time a decision was reached. Political inaction may have led to this dinosaur dying out entirely, unless some specimens were illegally removed at an earlier date.


All de-extinct species are known to have particular biopharmaceutical properties, though those specific to Coelurus are unknown. It also had potential as a biological attraction at Jurassic World, but how successful it would have been is not known since it was never exhibited successfully.


As a smaller and more lightweight dinosaur, Coelurus is not especially threatening. It is, however, very fast, and its carnivorous diet means that it has adaptations such as teeth and claws that it uses to attack prey. Humans are large enough to present a threat to it, though; it is unlikely a lone Coelurus would attack a human unprovoked.

It is probably possible to defend against an attacking Coelurus by physically fighting it off, grabbing it by the neck in the manner one would do with an aggressive goose. This ensures that the mouth can be kept at a distance. The hands and feet should also be kept away, and in general, once the animal is under control it could be tossed. Ensuring that this dinosaur sees you as a threat is probably enough to discourage it from attacking, since its fragile build gives it reason to be cautious already. Most animals can be intimidated by loud noises, bright lights, and exaggerated gestures.

Behind the Scenes

Coelurus was first introduced to the Jurassic Park franchise via Michael Crichton‘s original novel. It was named as being a species that was currently in the works, having yet to be produced. It was introduced to S/F canon through viral marketing with the Dinosaur Protection Group, which led to a toy being produced by Mattel for the Jurassic World: Fallen Kingdom line.