Segisaurus halli (S/F)

With a name meaning “Hall’s Tsegi Canyon lizard,” S. halli is the type and only known species of Segisaurus. The only known specimen of this coelophysid was discovered by a Navajo man named Max Littlesalt and a geology student named Robert H. Thomas in 1933 in Tsegi Canyon of the Navajo Sandstone Formation in Arizona, and is the only dinosaur to have ever been excavated from the site. It was described by Charles Lewis Camp in 1936, who omitted the ‘T’ at the beginning of the name of the canyon for which it is named. Its specific epithet honors A. Hall, a colleague of Camp’s and one of the leaders of the Rainbow Bridge and Monument Valley Expedition which collected the fossil. The single known fossil specimen is believed to belong to a subadult, which was found in a defensive curled-up position which theropod dinosaurs often take as an assumed self-preservation technique against sandstorms and ashfall.

Segisaurus lived during the Pliensbachian to Toarcian stages of the Early Jurassic period (between 190 and 174 million years ago) and was closely related to the more famous Coelophysis. It is known from only a single incomplete skeleton, which which lacks the skull and most of its dorsal and cervical vertebrae.

InGen recovered and identified DNA of Segisaurus sometime between 1986 and June 11, 1993. Due to the decay process affecting molecules of DNA over time, they were unable to reconstruct enough of the genome to create viable specimens before the 1993 Isla Nublar incident occurred. Samples from Isla Nublar were lost due to sabotage and environmental damage, but specimens salvaged from Site B prior to its evacuation were safeguarded by InGen. Sometime prior to the 2015 Isla Nublar incident, InGen had successfully cloned Segisaurus on Isla Nublar. The species is believe to have become extinct during the three years after the closing of the park.

Speculative depiction of Segisaurus from the Jurassic Park Institute. This is currently the only depiction of Segisaurus in the franchise, but its actual appearance is not known.

This small theropod is close to the size of a goose, at roughly one meter (3.3 feet) from head to tail, half a meter (1.65 feet) tall, and weighs between 4 and 7 kilograms. As the only known fossil specimen is thought to be a subadult, the full-sized animal may be somewhat larger. Segisaurus has an unusually large opening in the ischial portion of its puboischial plate (the lower region of the hip bones). It is a birdlike animal with a lengthy flexible neck and stout body, a long tail, and lanky forearms. The legs are also long and the feet have three toes each. Its collarbone is similar to a bird’s, and it has clavicles, unlike other dinosaurs of the early Jurassic.

The splint-like rib bones of the neck were hypothesized by Charles Lewis Camp, who named the genus, to be support structures for a patagium similar to that in the modern-day Draco lizards. This interpretation suggests that the flap-like neck patagia would make the dinosaur highly aerodynamic and allow it to run at incredible speed. Alternatively, such a structure could be used for thermoregulation or display.

The fossil skull of Segisaurus has never been found. The skull on the Jurassic Park brochure and other promotional material appears very compact with a short snout and overall tall shape, somewhat like that of an abelisaur. Conversely, the Jurassic Park Institute artwork depicts it with a more feasible coelophysid skull shape, with a long, low snout and narrow head.

The coloration of Segisaurus has also not been revealed. Artwork on the Jurassic Park Institute depicts it as a vibrantly-hued animal, with a red-orange neck and flanks and a teal belly. The teal color of its belly fades to blue-green on the upper legs, slowly darkening until it becomes a dark shade of blue on the lower legs and feet. On its flanks and back, the red-orange base color is striped in darker red; this continues to its tail and on the upper side of its neck. There is also dark red striping on the head, with a more vibrant red patch around the eyes and particularly noticeable dark red striping on the snout. These stripes become grayer on the lower jaw and on the tip of the snout; in particular, the latter appears completely gray. The arms, like the upper legs, are teal.


No growth stages of Segisaurus have been observed. The only known fossil specimen is believed to be a subadult, so the hatchling and adult stages are unknown.

Sexual Dimorphism

Because no specimens of this dinosaur have ever been observed, sexual dimorphism is unknown.

Preferred Habitat

The Navajo Sandstone Formation, where Tsegi Canyon is located, is located in an area that was once western Pangaea. It is believed to have been a landform called an erg, or a region of windswept flat sandy desert with little to no vegetation. It would have been affected by seasonal monsoons which occurred during the winter. Therefore, in prehistory, Segisaurus would most likely have preferred arid sandy regions.

Muertes Archipelago

InGen had reconstructed a Segisaurus genome with 48% viability, meaning it was not ready to be cloned as of the incident which effectively ended the Jurassic Park project. During the evacuation before Hurricane Clarissa, InGen personnel removed Segisaurus samples from the Isla Sorna facility for safekeeping. These samples were retained until successful cloning on Isla Nublar was possible years later, but there is no evidence that this species was ever introduced to Isla Sorna.

Isla Nublar

While Segisaurus was planned to be exhibited in Jurassic Park, InGen had not succeeded in cloning any before the incident beginning on June 11, 1993. At the time, the Segisaurus genome was 48% complete, meaning it was not yet viable. Specimens in the embryo storage units were destroyed due to sabotage; the insulated pipes delivering liquid nitrogen to the cold storage were severed, resulting in a rise in temperature which destroyed the embryos. Furthermore, after the abandonment of the island, unknown activity caused a pipe feeding the artificial pond in front of the Visitors’ Center to rupture; this caused structural damage to the building and resulted in one of the embryo storage units to buckle and collapse. Flooding destroyed the remaining specimens. As the stolen embryos were never successfully removed from the island, all specimens on Isla Nublar were lost.

InGen had planned a small paddock for Segisaurus on Isla Nublar located in the south. It would border the Jungle River to the north, and would be separated by the main tour road from the secondary Triceratops paddock on all other fronts.

Planned (orange) range for S. halli on Isla Nublar, as of June 11, 1993

Sometime prior to December 22, 2015, InGen succeeded in cloning viable Segisaurus under the guidance of Masrani Global Corporation. Population statistics remain unknown for the period of time during which the animal existed. It most likely inhabited habitats in Sector 5, in the north part of Isla Nublar; there is no evidence that it was ever exhibited in Jurassic World. Following the 2015 incident on the island, this species would have been able to escape its habitat into the wild.

A report published on February 4, 2018 by the Dinosaur Protection Group heavily implied that Segisaurus had become extinct on Isla Nublar.

Mantah Corp Island

The testing facility on Mantah Corp Island was perhaps the best candidate for keeping Segisaurus in captivity, having a large desert biome as one of its main habitats. However, there is no evidence that Mantah Corporation appropriated Segisaurus DNA or specimens during the years the facility remained in operation parallel to Jurassic World.

BioSyn Genetics Sanctuary

No living Segisaurus have been reported in recent years, so none are believed to have lived at the BioSyn Genetics Sanctuary or other facilities operated by BioSyn.

Black market

While it is possible that poachers could have removed living Segisaurus from Isla Nublar during the twenty-first century, there is no direct evidence that this occurred. Its DNA is believed to be the only form in which it remains, though with de-extinction technology going open-source in 2018, it is now possible for a person or organization of means to clone this animal again.

If genetic samples or specimens of Segisaurus are being traded behind closed doors, there is a good chance they will eventually turn up in the Amber Clave night market, the most globally noteworthy hub of de-extinct animal trafficking.

Wild populations

A poorly-known dinosaur, fossils suggest that Segisaurus existed in the early Jurassic period roughly 183 million years ago (though the time frame is debated by paleontologists). Only one fossil has been found so far, providing only limited information about its temporal range as well as its distribution. It is known to have inhabited the continent of Laurasia, living in deserts to the southwest. This species became extinct during the late Jurassic, but as so little is known about it, the circumstances that caused its extinction can only be speculated upon. During the end of the twentieth century, this dinosaur’s DNA was used to clone it, reversing its extinction.

There is no evidence that populations of Segisaurus ever made it off of Isla Nublar to establish in suitable habitats anywhere else in the world. It may have become globally extinct again.

Behavior and Ecology
Activity Patterns

The activity patterns of Segisaurus are unknown due to a lack of observations. It would be adapted to a hot desert environment, but how this impacts its activity patterns is purely speculative.

Diet and Feeding Behavior

Segisaurus is a carnivore, and paleontologists believe it feeds on insects, other invertebrates, and small vertebrate animals. Its feeding behaviors after being cloned by InGen are unknown.

Social Behavior

The social structure of Segisaurus is unknown due to a lack of observations.


As with all dinosaurs, Segisaurus lays eggs to reproduce. Other theropods (including most modern birds) are known to have cloacae, so presumably Segisaurus has a cloaca which it uses as a reproductive organ.

Theropods lay bird-like, ovoid eggs in numbers usually fewer than twenty. As one of the smaller dinosaurs, Segisaurus probably lays comparatively small eggs; its incubation period is therefore likely shorter than many other dinosaurs. Its eggs may hatch after incubation lasting a few weeks, like small birds.


Because no Segisaurus have been observed in the flesh at any point in the franchise, the vocalizations they may produce and other communication methods remain unknown.

Ecological Interactions

As a carnivore, Segisaurus would regulate the populations of its prey items. Because of its small size it could also be a prey item itself for larger carnivores. However, its ecological role on Isla Nublar after being cloned by InGen is unknown. As it was adapted to a hot and arid desert environment, it may not have fared well in the lush tropical climate the island provided. It probably competed poorly against Compsognathus, another tiny theropod with high levels of social activity and better adaptations to the tropics. This may have contributed to its likely extinction, though this is an unconfirmed hypothesis.

During its native Jurassic period, Segisaurus was affected by hematophagous (blood-drinking) parasites, possibly mosquitoes, which had evolved by that point in time. It is not known if it is similarly affected by modern parasites.

Cultural Significance

Segisaurus is an obscure genus and not well-represented in media. Its species name honors A. Hall, one of the leaders of the Rainbow Bridge and Monument Valley paleontological expedition.

In Captivity

Nothing is currently known about how this animal can be kept in captivity. InGen originally intended to house it near the shores of the Jungle River in an area also suitable for Triceratops, which prefers grassland and can adapt to both wet and dry areas. Since it was originally native to hot and arid deserts, it may not have flourished on Isla Nublar after it was eventually brought back from extinction.

If hypotheses about this animal having aerodynamic patagia are correct, it would be an extremely fast creature, among the swiftest dinosaurs. While it is small in size and mostly feeds on insects, its speed would make it difficult to recapture in the event of an escape. This makes it a potential security risk.


Paleontologists have only uncovered one fossil specimen of Segisaurus, but what has been discovered provides fascinating insight into not only the ancient ecology of the Navajo Sandstone Formation but also the evolution of theropod dinosaurs. It has very birdlike features to its skeleton, many of which are absent from other Jurassic theropods and did not become common until later. While the extremely birdlike theropods are often thought of as occurring in the later Jurassic and Cretaceous periods, the anatomy of Segisaurus demonstrates that such features actually evolved fairly early in the theropod lineage.

Structures in the neck of Segisaurus suggest that it would have had patagia similar to that of the genus Draco alive today. These may have made it more aerodynamic, helped it regulate its body temperature, or served as display structures. Since the species was made de-extinct sometime during the early twenty-first century, it is possible that InGen scientists were able to determine whether this dinosaur really had patagia and, if so, what purpose they served. We can only hope that this information is eventually released to us.


This species’s future was put up for debate between 2017 and 2018, during which time Isla Nublar’s ecosystem was threatened by volcanic activity centered on Mount Sibo. World governments and Masrani Global Corporation largely opposed saving the animals, while the Dinosaur Protection Group and a smaller number of governmental and civilian interests supported saving them. Public opinion was split; some favored saving only herbivorous animals, leaving the carnivores to die. This would have allowed Segisaurus to become extinct. Ultimately, the non-action policy was made official, and rescue attempts were made against government order. Segisaurus is not believed to be among the species saved from the island; it may have already become extinct by early 2018.


Originally, InGen intended Segisaurus to be an attraction in Jurassic Park. It would have been visible from the main tour and Jungle River Cruise. After this animal was cloned by InGen under Masrani Global Corporation, its interactions with humans remain unknown. It does not appear to have been exhibited in Jurassic World.

Due to a combination of genetic engineering and evolutionary time, de-extinct life forms possess biopharmaceutical properties that are not known in naturally-occurring modern species. However, the particular compounds that could be obtained from Segisaurus are presently unknown.


Since no Segisaurus have been directly observed, it is not entirely clear what kind of danger one might present. They can be assumed to be not too different from other very small theropods, such as the better-studied Compsognathus, and can probably be dealt with in a similar manner.

Defense techniques used against aggressive waterfowl such as geese and swans might also be useful, since they are modern-day dinosaurs of similar size that an average person probably has more experience around. These birds can be defended against by grabbing them by the neck and holding them away at arm’s length, keeping the beak and limbs away from your body, and then throwing them away from you.