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 became extinct during the three years after the closing of the park.
This small theropod was 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 weighed between 4 and 7 kilograms. As the only known fossil specimen is thought to be a subadult, the full-sized animal may have been somewhat larger. In real life, Segisaurus has an unusually large opening in the ischial portion of its puboischial plate (the lower region of the hip bones). It was 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 genus. 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 have been used for thermoregulation.
In real life, the 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. In real life, the only known specimen is believed to be a subadult, so the hatchling and adult stages are unknown.
Because no specimens of this dinosaur have ever been observed, sexual dimorphism is unknown.
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 real life, Segisaurus would most likely have preferred arid sandy regions.
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.
Sometime prior to December 18, 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.
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 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.
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.
Behavior and Ecology
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 impacted its activity patterns is purely speculative.
Diet and Feeding Behavior
Segisaurus was a carnivore, and paleontologists believe it fed on insects, other invertebrates, and small vertebrate animals. Its feeding behaviors after being cloned by InGen are unknown.
The social structure of Segisaurus is unknown due to a lack of observations.
As with all dinosaurs, Segisaurus would lay eggs to reproduce. Jurassic Park: The Game depicts all of its dinosaurs with cloacae, so presumably Segisaurus would have a cloaca which it used as a reproductive organ.
Theropods lay bird-like, ovoid eggs in numbers usually fewer than twenty. As one of the smaller dinosaurs, Segisaurus probably laid comparatively small eggs; its incubation period was therefore likely shorter than many other dinosaurs. Its eggs may have hatched 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 have produced remain unknown.
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. This may have contributed to its 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 was similarly affected by modern parasites.
Interactions with Humans
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.