Allosaurus jimmadseni (S/F) / (S/F-JWE)

Allosaurus, meaning “different reptile,” is a genus of large carnivorous theropod dinosaur in the family Allosauridae. It lived during the Kimmeridgian and Tithonian ages of the late Jurassic period, approximately 155 to 145 million years ago, and is known from western North America as well as Portugal and potentially other parts of the world. The type species is A. fragilis; the species name references the fragile nature of its fossilized remains. The genus name Allosaurus describes the concave shape of its vertebrae, which was unique when the animal was first identified in 1877. However, the species that was cloned by International Genetic Technologies is now believed to be A. jimmadseni, which is named in honor of paleontologist James Henry Madsen.

The earliest fossils of Allosaurus were tail vertebrae found in the Morrison Formation of Colorado by geologist Ferdinand Vandeveer Hayden in 1869, who sent them to Joseph Leidy for study. They were variously assigned to several preexisting genera of dinosaur until paleontologist Othniel Charles Marsh named them in 1877 during the Bone Wars. Due to the intense competition between Marsh and his rival Edward Drinker Cope, many Allosaurus specimens went undescribed during the late 1870s and 1880s. In 1920, Charles W. Gilmore clarified many of Cope and Marsh’s findings and consolidated numerous fossil genera into Allosaurus. Since then, paleontologists have identified many Allosaurus fossils from the Morrison Formation, giving modern science a large body of knowledge about this animal; remains were also found in Montana, New Mexico, Oklahoma, Wyoming, South Dakota, and Utah.

While the most common species by far is Allosaurus fragilis with over seventy individuals known, there are several other species. Allosaurus europaeus was identified from the Lourinhã Formation in Portugal in 2006. In 2020 the species Allosaurus jimmadseni was identified from the Morrison Formation in older rocks than A. fragilis; aside from their age, these two can be told apart by the straight lower margin of the cheekbone on Allosaurus jimmadseni. Two other species, Allosaurus amplus and Allosaurus lucasi, are known from North America as well. Some possible remains have been reported from the Tendaguru Formation in Tanzania, though these are no longer thought to belong to Allosaurus or any allosaur. More questionable remains have been presented from Siberia and China.

International Genetic Technologies, Inc. obtained Allosaurus jimmadseni ancient DNA from blood-drinking invertebrates such as mosquitoes preserved in late Jurassic amber samples. As of 1993, the genome was 12% complete; the animal would not be cloned until the twenty-first century, at which point InGen was owned by Masrani Global Corporation. The species is identifiable based on its size and the shapes of its skull features. At the time it was cloned, it was still classified as Allosaurus fragilis.


Among the larger theropods, an adult Allosaurus may grow to around 28 to 40 feet (8.5 to 12.1 meters) from snout to tail and 12.5 to 14 feet (3.8 to 4.2 meters) tall when standing upright. This makes InGen specimens noticeably larger than their fossil counterparts. An average animal weighs 1,500 pounds (700 kilograms), but when they are fully grown, they can easily be as heavy as 4,400 pounds (2,000 kilograms) with a maximum reported weight of 4,500 pounds (2041 kilograms). At this size, it is an apex predator, and has many evolutionary adaptations to match.

Mature female Allosaurus

The massive head (slightly wider in InGen specimens than in fossils) is distinctive, with a long snout and large nostrils giving it an excellent sense of smell; of particular note are the thin triangular horns on its head, which are sheathed in keratin and formed from the lacrimal bones. Leading to the horns are a pair of low ridges extending to the nasal bones. Fossil evidence suggests that the size and shape of the horns would vary from one animal to the next, making them easy ways to identify a particular Allosaurus. Like most theropods, it has a powerful jaw with sharp, serrated teeth; it has five teeth in each premaxilla and fourteen to seventeen teeth in each maxilla. The jaws can open impressively wide, up to ninety-two degrees, and are designed for tearing or hacking off pieces of flesh from prey. However, this means that its bite force is lesser than that of many other large theropods. Its eyes are average-sized for a theropod, with yellow sclerae and round, birdlike pupils. Like most theropods it has nictitating membranes to protect its eyes, originating from the medial canthus. Allosaurus has better-developed sinuses than more primitive theropods such as Ceratosaurus, giving it a good sense of smell. Its tongue is not particularly thick, but is pointed, and very dark blue or almost black in color.

Tough skin consisting of small scales covers the body surface of Allosaurus, and the whole body is lean and muscular. The neck is short and strong, and dorsal spines decorate much of the body’s length from neck to tail. While its forelimbs are short, as with many theropods, they are longer and far stronger than those of Tyrannosaurus and bear three-fingered hands. Each finger ends with a long curved and pointed claw, a formidable weapon in combat in addition to the powerful jaws. The thumb is the largest of the digits. It is able to pronate its wrists, as can most of InGen’s theropods, but adults are sometimes seen to hold their hands in a supinated position like their fossilized ancestors would have.

The legs, while not designed for speed to the degree that tyrannosaurs’ legs are, can still propel the animal along at speeds of 19 to 34 miles per hour (30 to 55 kilometers per hour). The main hip bone, or ilium, is massive. The legs are shorter than those of tyrannosaurs, and three of the toes bear less developed and more hoof-like claws. The fourth toe, the dewclaw, does not reach the ground; the skeleton shows signs of a fifth toe which has been lost. The tail of Allosaurus is slightly downward-sloping, and comprises about a third of the animal’s overall length.

Coloration in this species is generally subdued, as suits an ambush predator. The body is largely tan or gray, with dark blue colors on the dorsal side. Mottled gray colors may be interspersed with faded dark gray, blue, or yellow stripes; the lacrimal horns are often dull red or orange, but in females, they are the same color as the dorsal body. Yellow rings may decorate the eye orbits of this animal and white markings may occur on the face, and the underbelly is typically a slightly lighter color than the rest of the body.


At the hatchling stage, this theropod shows a proportionally larger head than the adult, a feature that is common to many baby animals. The lacrimal horns start out quite short, elongating as the animal nears adolescence. Integument is variable and may change as the animal grows; baby allosaurs may demonstrate scaly skin, a limited coat of feathers, pebbly skin, a combination of pebbly skin and spiny quill-like protrusions, or a combination of fluff and scales. By the time they are adolescent, they are fully scaled.

Hatchling and juvenile Allosaurus growth stages and variants. Concept art by Ralph Herrera.

Juvenile Allosaurus can be told apart from adults by their anatomy. In juveniles, the lacrimal horns point sharply backwards; as the animals mature their horns become more vertically shaped. The juvenile’s body is smooth, with no distinctive features to speak of other than the lacrimal horns. In the adult, raised spines develop along the backbone from neck to tail, likely serving as display features and giving the animal a more rugged appearance. The jaw also develops, becoming more prominent, and the lacrimal horns fill out and grow to become upward-pointing. In juveniles, the legs are comparatively longer than adults. During their adolescence they undergo numerous body changes, and may be irritable and behave erratically.

The growth rate of this animal is not entirely known, but most of them at Jurassic World were still juveniles in 2018. The latest they could have been cloned was late 2015, meaning adolescence is reached in a minimum of two to three years when under the effects of growth supplements. After the adolescent stage is reached, the transformation into a mature adult takes less than a year; a juvenile female which escaped into the wild in the summer of 2018 was fully-grown by the spring of 2019. Fossil evidence suggests that the animals naturally reach full size in fifteen years, with a lifespan of around 22 to 28 years.

Sexual Dimorphism
Juvenile male Allosaurus. Note the red lacrimal horns and the lack of spines or raised scales on the body.

It is believed that the males always have the red coloration of the lacrimal horns, while most females lack this color, but there is some dispute about this. The only definite form of sexual dimorphism in Allosaurus is body size. According to an unconfirmed size chart supposedly used for reference in the production of Jurassic World: Fallen Kingdom, the female grows noticeably larger than the male.

Authorities from the Department of Prehistoric Wildlife have suggested that the color differences in Allosaurus may represent sexual dimorphism (with males exhibiting the bluish skin, yellow stripes, and red crests), but acknowledge that not enough research has been performed to determine whether this is the case. Allosaurs may show individualistic color variation due to genetic engineering or natural genetic variance, making it harder to tell. Still, all confirmed males of this species have had red horns and yellow stripes, while all confirmed females have had darker blue skin with tan countershading.

Preferred Habitat

An ambush predator, the Allosaurus is at home in forested areas; the deeper the forest, the more comfortable this animal will be. Its speed does allow it to do well on open plains. It has been known to voluntarily move into redwood forests, which provide it with cover as well as maneuverability. Allosaurus is commonly seen near mountainous regions, but is not known to climb far uphill; instead, it is typically seen in the valleys between mountain ranges. It can tolerate tropical climates as well as the cooler temperatures of the Pacific Northwest.

Muertes Archipelago

De-extinction research and development originally took place on Isla Sorna in the late 1980s and early 1990s. However, Allosaurus did not exceed 12% viability during that time. There is currently no evidence that this animal ever lived there or elsewhere in the Muertes Archipelago. Since activity on the island is kept well-hidden by its owners, it is unknown if any breeding is currently taking place.

Isla Nublar

Allosaurus was cloned by InGen on Isla Nublar sometime before December 2015 with the intent to be exhibited in Jurassic World. However, the park closed before these animals could be successfully put on display; in the intervening time, they were maintained in habitats in Sector 5 in the island’s north.

After the 2015 incident, artificial barriers were deactivated and animals were permitted to roam the island at their leisure. Between 2015 and 2018, Allosaurus were known to roam the Western Ridge near the gondola lift as well as near Mount Sibo. On June 23, 2018, three juvenile males were sighted near Mount Sibo; one was confirmed killed when it was struck by a large pyroclast, and the others likely perished due to the volcanic eruption or drowning. Two juvenile males, one juvenile female, and one adult were removed from the island via the S.S. Arcadia. This means that prior to the eruption, there were a total of at least seven Allosaurus on Isla Nublar, including five juvenile males, one juvenile female, and one adult of presently unconfirmed sex.

One of the juveniles removed from the island was logged into the ship’s manifest at 13:44 and cosigned by Charlie Hound, held in Container #30-1011-2042 (Cargo #22160). It was weighed at 1,115 kilograms and was highlighted in green, potentially indicating good health. The adult was held in Container #25-1006-3720 (Cargo #65549) and cosigned by Rob O’Day, logged into the manifest at 13:41 and weighed at 2,250 kilograms, making it exceptionally bulky for its species.

Mantah Corp Island

InGen’s rival, Mantah Corporation, stole numerous species of de-extinct animal from Jurassic World facilities in the 2000s and 2010s, housing the animals and breeding new ones at a facility on Mantah Corp Island. However, Allosaurus was not confirmed among their menagerie.

BioSyn Genetics Sanctuary

Allosaurus were known from around the world after the events of 2018 allowed de-extinction technology to go open source, and escapees were common. BioSyn Genetics was allowed by several nations’ governments to capture wild dinosaurs and transport them to secure facilities where they could be kept safely away from people. In Italy, the company headquarters were located alongside the BioSyn Genetics Sanctuary, its largest such facility. Allosaurus was among the species contained there.

None were seen in early 2022, so it may be that this dinosaur in particular was not introduced to the valley until after the United Nations took over operations from BioSyn. At least one adult was released from the Amber Clave fighting pits in Malta and was likely captured by authorities afterward, with BioSyn Valley being its likeliest destination.

Black market

During the night of June 24, 2018, three juvenile and one adult Allosaurus were transported to the Lockwood estate near Orick, California to be sold on the black market. One juvenile male (weighed at 1,115 kilograms or 1.2 tons) was sold to a currently-unknown bidder and was transported along with several other cargoes away from the estate, last seen near Monument Valley in Utah. The others, including one adult (weighed at 2,250 kilograms or 2.5 tons), a juvenile male, and a juvenile female, were released into the surrounding forest that night by Maisie Lockwood to avoid the animals dying of hydrogen cyanide inhalation.

After being released into the wild, and having their DNA sold during the auction (possibly to Anton Orlov, a notorious Russian mobster), this dinosaur has retained a presence on the black market. It is among the species known for being featured in the Amber Clave fighting pits; adults and juveniles, both males and females, have been spotted being forced to fight for the entertainment of paying customers. In 2022, an adult female was released from the Amber Clave and was seen wandering the streets of Valletta. A juvenile which had been fighting shortly before was not seen and may have died in a forced fight with a Baryonyx. The adult which escaped had been intended for a fight with a Carnotaurus that July 30, but after both of these animals ventured out into the streets, they appeared to enjoy each other’s company instead.

Wild populations

Allosaurus was native to the continent of Laramidia during the late Jurassic period, inhabiting seasonal floodplains and prairies. While fossils indicate that its genus ranged from North America through the larger European islands, the species A. jimmadseni in particular lived in central North America exclusively. This dinosaur evolved about 155 million years ago, persisting for around ten million years before environmental changes caused its extinction. 145 million years later, it was cloned by scientists using revolutionary genetic engineering techniques.

The first allosaurs re-introduced to North America were in June 2018, including at least two females and one male, were released from a black market auction into the Pacific Northwest near Orick, California. They seem to have mostly stayed near the area; a fourth (one of the juvenile males) had been transported, but was sold to an unknown buyer. In June 2019, a female Allosaurus was confirmed to be present in Big Rock National Park in northern California. It is believed to have been one of the juveniles released from the Lockwood estate, rather than the adult. By this time, it was fully grown; as of that month the U.S. Fish and Wildlife Service was tracking it with the intent to capture, along with a possible second individual. The female involved with the Big Rock incident can be identified by its blind right eye. A second allosaur, a male with both eyes intact, was sighted there the following day. In the early winter of 2020, a juvenile allosaur was found in Yosemite National Park; it was captured by rangers and moved to a more suitable (and undisclosed) habitat. In early 2022, this theropod was reported to have a presence established in the U.S. state of Nevada, near the southern end of the state and close to the California border; the previous year the CIA had tracked them in northern Idaho as well. By the end of May, a subadult had been sighted near Devils Tower in Wyoming, having menaced a hiker at night. A juvenile was sighted along a road in Morelos, Mexico on May 13. The DPW dispatched agents to investigate, but it is unknown whether it was relocated. Another was sighted on May 29 one minute after midnight by a trail camera at Grand Mesa in Colorado, while yet another was seen on June 8 in Crater Lake, Oregon. The game Jurassic World Evolution 2 depicts one male Allosaurus being taken by poachers to a remote camp located in the North Cascades in Washington State, though it broke free of captivity and killed its captors along with innocent bystanders. It can be recaptured by the U.S. Fish and Wildlife Service in the course of the game, its wounds treated. It is then subsequently transported to the Dinosaur Housing and Transport Hub, operated at the USFWS headquarters in the Pennsylvanian Appalachians. Additionally, both of the Allosaurus from Big Rock can be captured and transported to Yosemite National Park where they can be safely housed.

While most modern Allosaurus populations are located in North America, not all of them live there. Animal trafficking and illegal breeding have allowed them to proliferate into other parts of the world, and captive specimens often escape. Footprints attributed to Allosaurus were spotted early in 2022 on the shores of Lake Nasser in Egypt, reported to the Department of Prehistoric Wildlife. This followed reports from the CIA’s dinosaur tracking division of Allosaurus living along the Nile River in Sudan, possibly a part of the same population later suspected near Lake Nasser.

While uncommon, they have been seen in countries bordering the Indian Ocean. In India itself, they are found in the central part of the fertile Indo-Gangetic Plain and its surroundings. Australia has a population of its own too, found in the southwest near ephemeral bodies of water such as Moore River. This is a harsh environment during the dry season, but not beyond the adaptability of this hardy dinosaur.

By mid-2022, an Allosaurus was confirmed in Santa Croce Camerina, Italy. Local residents were aware of its presence and no known efforts were in place to relocate it. Aside from captive specimens on the black market, this was the first Allosaurus confirmed in Europe.

Behavior and Ecology
Daily Activity

Allosaurus appears to be cathermal, active at times of day and night. At least one female released into human-occupied parts of the state of California has been seen hunting during the night, likely a means to avoid humans. This same animal has been seen active during the day when disturbed by human activity, but it appears to have a preference for nocturnal activity patterns.

Diet and Feeding Behavior

As with most theropods, the Allosaurus is a carnivore. In its native late Jurassic period, it was the apex predator in its environment, and today still maintains a competitive edge over many other predators it has been introduced alongside. The main weapons of this animal are its powerful jaws and sharp teeth, which are used to pierce the hides of prey items and tear out large pieces of flesh. If a victim survives the initial bite, it is likely to bleed out, making it easy for the allosaur to finish it off. The bite force of this animal is weaker than that of tyrannosaurs, a compensation for its ability to open its jaws astonishingly wide. On occasion, this animal may congregate in loosely-organized packs with no real authority or hierarchy to mob larger prey items.

This animal is capable of pursuit hunting, but excels at ambush, which is why it is often found in forested areas. Adults, with their proportionally shorter legs, are best suited to ambush hunting when compared to the longer-legged juveniles. Younger animals are better at chasing their prey down. Its subdued coloration helps it to avoid being seen; it will use its excellent senses of smell and hearing to locate prey, quietly move in on it, and then make a sudden attack. Since it does not rely heavily on eyesight to track prey, it can hunt quite well at night. Its ambush tactics and predatory adaptations make it one of the most efficient theropod hunters, and is is known to take down prey larger than itself. Known prey items include Nasutoceratops and possibly Gallimimus, though the latter is far faster than the allosaur and likely a difficult prey item to catch. Deleted scenes have shown it attempting to prey on juvenile Triceratops. On occasion, they have also targeted humans as prey. It is a vicious brawler against even formidable foes and will weaken its enemies by wounding them. For example, an adult female allosaur was witnessed in 2019 using the talons on its toes to make gashes in the side of a Nasutoceratops, an attack which would result in blood loss and shock to the intended prey.

According to the game Jurassic Park: Operation Genesis, its favored prey species is Stegosaurus, which it would have lived alongside during prehistory. However, the species featured in this game is not A. fragilis or A. jimmadseni, but rather the dubious “Allosaurus tendaguruensis,” which is now believed to be a different theropod altogether.

It is worthy of note that the Allosaurus, even as an adult, has been witnessed targeting the young of other animals rather than mature individuals when possible. An adult female Allosaurus in 2019 was observed using a loud roar to disorient and frighten a mother Nasutoceratops, causing the horned herbivore to leave its offspring temporarily unguarded. The aforementioned 2018 deleted scene would have featured a subadult allosaur targeting a young Triceratops during a stampede. In both cases, however, the allosaur was unsuccessful, as the prey’s parents intervened.

Allosaurus is a persistent predator, known to push its way through many kinds of obstacles if it believes the reward of prey is worth its struggle. It is, however, pragmatic: it recognizes when the risk to itself outweighs the reward of food, and will back down if it faces a challenge that is not worth its efforts. While Allosaurus frequently risks injury during the hunt and often sustains wounds during combat, it will not do so unnecessarily. If a prey item puts up too much of a fight, the allosaur will try its luck elsewhere.

Social Behavior
Juvenile male Allosaurus sold at auction, 6/24/2018. Its buyer is currently unknown.

This theropod appears to be mostly solitary, though juveniles seem to be more tolerant of company than adults. Little is known about their social behaviors, as only a few field observations have been made (and even fewer under normal conditions). The red-colored lacrimal horns of juveniles suggest a social function, especially when contrasted with the gray color of the body. Fossil evidence suggests that the lacrimal horns vary in size and shape from one animal to another, also implying that they serve social functions. In some adults, the horns of adults lose their red color; this implies that social behaviors change from adolescence to adulthood, possibly with the animals becoming increasingly solitary as they age in a manner similar to modern-day ravens. Allosaurus adults only seem to congregate during the mating season, and nest in groups.

According to the mobile application Jurassic World Facts as well as various other mobile games, the Allosaurus will on occasion form packs with its own kind for the purpose of hunting larger prey items. Despite this, it is not a naturally social animal, and these packs lack a social hierarchy or organization. They most likely disband after the hunt concludes.

The anatomical changes from adolescence to adulthood also include the formation of spikes and raised scales in all individuals. This gives the animal a more rugged and intimidating appearance, which likely serves to warn away rival allosaurs as well as competitor species.


All dinosaurs lay eggs to reproduce. The Allosaurus most likely possesses a cloaca which houses the reproductive organs of both the male and female. Cloacae have been observed in other theropod species. While the red lacrimal horns may be used as display features, at least some of the adult females lose the red color as they mature. Instead, the spines and raised scales which occur in the adult are more likely to be used to advertise maturity, fertility, and overall health to potential mates. The male may possibly retain the red color and use the horns to display, as well as being more colorful overall, but this is not entirely understood. This dinosaur breeds during the early spring to midsummer, congregating in groups to mate and nest.

Color variants of Allosaurus jimmadseni in the early juvenile stage. Concept art by Ralph Herrera.

Theropod eggs are birdlike, being ovoid in shape, which is an evolutionary adaptation to prevent them from rolling around too much. A larger theropod such as Allosaurus would have an incubation period lasting roughly six months. Most theropods display parental care, but it is not known if both parents help to raise the young or if only one does; in any case, by the time the animal reaches adolescence, it no longer requires parental care to thrive and is able to hunt on its own.


As with many theropods, the Allosaurus cloned by InGen are most likely more vocal than their ancestors were capable of; nonetheless, they seem to have adapted well to their increased vocal capabilities. They can be heard emitting loud low-pitched bellows and deep growls to warn away threatening rivals or animals which get in their way. During hunts, an Allosaurus may suddenly roar to frighten a prey item and cause it to misstep, giving the allosaur an opportunity to attack.

Body language is also used to communicate with other species, and most likely one another. Gaping the jaws and assuming a threatening position can be used as an intimidation tactic, while an irked allosaur may shove or snap at other animals to warn them away. While it has not been directly observed, body features such as the lacrimal horns are most likely used for communication, such as identifying a particular allosaur.

Ecological Interactions

Despite its aggressively predatory nature, the Allosaurus can live alongside a wide variety of other animal species. Many of its neighbors on Isla Nublar between 2015 and 2018 included animals that it would naturally have encountered during the Jurassic period, such as Apatosaurus, Brachiosaurus, and Stegosaurus. There is significant fossil evidence suggesting it preyed upon the latter, though sauropods are likely too big for a single allosaur to kill.

Mature female Allosaurus threatens campers, Big Rock National Park, CA (4/21/2019)

Other herbivorous animals in its territories on Isla Nublar included the hadrosaurs Parasaurolophus and (prior to its extinction) Edmontosaurus as well as the pachycephalosaurs Stygimoloch and Pachycephalosaurus, which would have been suitable prey. The heavily-armored Ankylosaurus would have presented more of a challenge, as would the fleet-of-foot omnivore Gallimimus and the tiny, elusive Microceratus. Several species of ceratopsians are known to live in similar territories to Allosaurus, including Triceratops, Sinoceratops, Nasutoceratops, and possibly Pachyrhinosaurus. The juveniles of these horned herbivores are known to be potential prey for Allosaurus, though the adults present it with a challenge that it may not be able to overcome. When it preys upon any of these animals, the allosaur acts as a regulator for their populations, which in turn benefits the plant life in its territory. This permits the allosaur’s feeding grounds to grow denser forests and undergrowth, which the allosaur benefits from.

Allosaurus may compete for food and territory with other theropods such as Carnotaurus, though when resources are abundant they may cohabit without issue.

This animal has been known to live alongside many carnivorous species as well. Potential competitors include Carnotaurus and Tyrannosaurus, which were most likely its biggest threats; it would have lived near the smaller Metriacanthosaurus on Isla Nublar before that species became extinct. It also lived alongside fish-eating Baryonyx and the pterosaurs Dimorphodon and Pteranodon; since Allosaurus seldom feeds on fish, it would not have had difficulty coexisting with these animals. It is large enough that Velociraptor is not a major threat, especially as raptors have become exceedingly rare due to human intervention. The Compsognathus is one of the smallest de-extinct theropods, and while it can be found in the same areas as Allosaurus, it is unlikely to ever be more than a nuisance to adult allosaurs.

While allosaurs are tolerant of other animals inhabiting their territories, their lives as neighbors are often less than harmonious. Other than hunting and killing animals in the areas surrounding their homes, Allosaurus can become defensive of their personal space and will attack and chase away other animals when stressed. During the 2018 eruption of Mount Sibo, a juvenile Allosaurus was seen snapping at a Gallimimus which had run too close during a stampede and giving an aggressive display to a gyrosphere. (In the original cut of the film, the Gallimimus accidentally bumps into the allosaur and is roughly shoved aside in response; for unknown reasons, this was changed so that the animals do not make physical contact in the scene.)

In the Jurassic period, Allosaurus was affected by hematophagous pests such as early mosquitoes, which is how InGen was able to obtain its DNA. No studies have currently been performed to determine whether modern mosquitoes affect it in a similar way.

The game Jurassic World: Evolution portrays it as being a host for the bacterium Campylobacter, which may cause campylobacteriosis. This bacterium is known to affect up to 100% of certain poultry populations.

Cultural Significance

Allosaurus is one of the most famous North American theropods (though its remains are also known from Europe) and is particularly well-known from the United States. It is considered one of the most popular American theropods, though it is still overshadowed by Tyrannosaurus rex, and is often depicted in art. Though not the number-one most famous dinosaur found in the United States, it is often portrayed as one of the most quintessentially American dinosaurs: many fossils have been found with various injuries, leading to it being stereotyped as a creature that took risks, faced hardship, and died young after spending its life fighting to survive.

Having been brought back from extinction and now released into the wild as of June 2018, it has also become one of the major faces of the de-extinct animal rights debate. Following an attack on campers in northern California in 2019, feral populations of Allosaurus have become one of the common symbols of de-extinct animals as a threat.

This particular species of Allosaurus is named in honor of paleontologist Jim Madsen. Its former synonym Allosaurus fragilis is the state fossil of Utah, where many specimens can be found, since 1988.

In Captivity

Like all of the large theropods Allosaurus is a difficult animal to keep in captivity owing to its size, habitat requirements, and stimulation needs. It is an active predator, and must be regularly supplied with meat; most carnivorous dinosaurs will eat livestock. Most captive theropods are fed both prepared meat and live prey, ensuring that they get their necessary nutrition as well as the stimulation provided by hunting and killing their own food. Because of its large size and aggressive behavior patterns, it should only be handled by experts.

Because none were ever successfully exhibited, little information has been released about its requirements in captivity. The only available information for the moment is what is known about this animal’s behavior in the wild.


Allosaurus is one of the best-known theropods, with many fossils being discovered in North America and Europe, and has given paleontologists detailed looks not only at its anatomy and evolutionary placement but also the behaviors of ancient theropods and their role in ecosystems. The remains of Allosaurus that have been found often show what kinds of injuries they sustained, which help demonstrate the types of interactions they had with other animals. These prove, for example, that Allosaurus actively fought with some of the large herbivores in its habitat. Such fights probably represent hunts, meaning this animal attacked and killed live prey.

Fossils of Allosaurus are a common sight in natural history museums, especially in the United States where this dinosaur was highly common. It is an excellent ambassador for science communication with the public, since it is easily accessible to anyone who visits a museum, and is often reconstructed in exciting poses. The fact that fossils suggest this animal really did live a dynamic life lends some credence to these dramatic reconstructions, making them based in science rather than pure speculation. Specimens with easily-recognizable injuries, such as “Big Al,” are often the subject of books and documentaries, with scientists attempting to determine what the animal’s life was like based on the injuries found in its fossil.

This was among the many species brought back from extinction by International Genetic Technologies during the time that Jurassic World operated between 2005 and 2015. While it was never successfully exhibited, it had been a desired specimen for decades; InGen had been trying to clone this species since at least 1993. Even though these efforts never quite met with success, the dinosaur’s genome was at least sequenced, adding one more branch onto the phylogenetic tree of InGen’s genetic library.


After being released onto Isla Nublar following the closure of Jurassic World, this species’s existence was up for debate in the courts and on the streets. Volcanic activity began on Isla Nublar in early 2017 and continued to build up over the course of the following year, culminating in a massive eruption in June 2018. Legal and ethical controversy surrounded these events, with organizations such as the Dinosaur Protection Group campaigning to have the animals safely relocated to a new habitat. The status of Allosaurus as a predator made it particularly controversial, since some people had suggested saving only the herbivorous animals (under the false impression that these animals are safer than carnivores).

Allosaurus was among the less propagandized species during the Mount Sibo controversy, with relatively little mention of it by the Dinosaur Protection Group. It was featured in at least one piece of promotional artwork in which it was used to illustrate the idea of many dinosaur species living in harmony.

Allosaurus featured in DPG artwork.

Ultimately the U.S. government opted to do nothing, since the park was private corporate property, and Masrani Global also chose to take no action. Allosaurus among other de-extinct organisms was illegally relocated to the mainland during the eruption, and at least one was sold on the black market to unknown buyers on June 24. It was last known to be within the United States, being transported through Monument Valley, but its ultimate destination has yet to be found. Others were released into the wild; at least one was involved with an altercation at Big Rock National Park in 2019, further fueling the debate as to how Americans should deal with these animals’ presence. The animal was driven away from the campers by being shot in the right side of the face with a double crossbow, but lingered around the area the following day while the U.S. Fish and Wildlife Service attempted to track it down. News reporter Rebecca Ryan covered the Big Rock incident but was unable to complete her report when an allosaur (a second individual, as it appeared to be a juvenile male and had both eyes intact) was chased through the area by a Fish & Wildlife helicopter. Her news van’s driver is believed to have died during these events.

Allosaurus is the state fossil of Utah, being designated in 1988.


This dinosaur was originally bred as a park attraction. InGen originally intended to exhibit Allosaurus in Jurassic Park, but by 1993 had not reconstructed enough of its genome to bring viability past 12%. The animal got a second chance in the twenty-first century with Jurassic World, but none of them are known to have been put on exhibit by the time the park closed in late 2015. It is unknown what kind of attraction this dinosaur would have been shown in, but large predators are always considered highly entertaining among thrill-seekers.

Although it was never shown to the public in a park, Allosaurus is still valued for the biological products that can be derived from it. All de-extinct animals are sources of unique biopharmaceuticals, which can be used to manufacture new types of medications. The specific pharmaceutical use of Allosaurus has not yet been explored. In addition to this, it is useful to science as its de-extinction has added to InGen’s genetic library. A juvenile male Allosaurus was, along with several others of its kind, captured in 2018 by Ken Wheatley at the behest of Eli Mills in order to sell on the black market; while the motives of its buyers are not currently known the animal sold for about U.S. $11,000,000. This money was intended to be used to finance the work of Henry Wu. In addition, a DNA sample was sold to a Russian buyer among eleven other samples; the buyer is suspected to be Anton Orlov. Multiple Allosaurus have been confirmed on the black market as of 2022, including juveniles. Some have been confirmed in the Amber Clave, an underground night market in Malta known for its fighting rings; Allosaurus are among the dinosaurs forced to fight to the death in these cruel spectacles.


This is a large carnivorous theropod, and should be treated with the utmost caution and respect. Allosaurus inhabits forested regions where it can easily stalk and ambush its prey: take care when traveling in remote woodland, especially in the Pacific Northwest where this animal is known to live, and do not travel alone. Be especially careful during the spring and summer months when Allosaurus are breeding, as they will defend their nesting sites. Should you spot this animal, stay as far away as you can, and back away slowly rather than running. The more panicked and afraid you appear, the more likely it will be to attack. Do not turn your back to it, and bear in mind that it may not be alone.

If the dinosaur is hunting, it may start to chase you. It is fast enough to outrun you, and juveniles are faster than adults; you are better off finding a sheltered place to stay out of reach, such as a tree or small cave. It is a poor climber, so putting a cliff between you and it may also help. Isla Nublar survivor Ben Pincus evaded an Allosaurus attack once by leaping off a waterfall (albeit accidentally). Stay where it cannot reach you until it moves on in search of easier prey. Vehicles may provide limited shelter, but it is best not to rely on this unless no other options are around; an adult Allosaurus is strong enough to flip over and tear open most commercially-available vehicles, which are generally not built to withstand that kind of attack. If it is impossible to escape or hide from an attacking Allosaurus, your best bet for survival is the same as it is with any carnivore: make yourself as inconvenient to eat as you can.

A family in 2019 had success at driving away a hunting Allosaurus this way. They utilized the rudimentary weapons available to them, such as debris and a fire extinguisher, to keep the dinosaur at bay. Ultimately it was driven away when one of the family members shot it using a double crossbow. If you must fight this dinosaur, aim for sensitive regions such as the eyes, ears, and nose. The family of campers in the Big Rock incident did everything correctly: they took shelter when advised to do so by park rangers, and when the dinosaur attacked them after being drawn to the sound of their baby crying, the family stayed together to defend one another. All predators will target solitary or otherwise defenseless prey when available, so there is strength in numbers. The animal finally backed down when it was injured. Remember that the family in this incident had no prior experience defending themselves from large theropods: they simply followed the steps experts advise for self-defense against extant carnivorous animals. You can greatly increase your chances of surviving an attack by taking these same steps: take shelter, stand together, fight back.

Should you be bitten or otherwise wounded, seek medical attention immediately. Along with blood loss and other physical damage, theropod bites can transmit sepsis-causing bacteria intended to kill prey that manages to escape.

Behind the Scenes

Adult and juvenile Allosaurus were apparently designed for the film Jurassic World: Fallen Kingdom, but ultimately only the juveniles appeared. An adult is known to have existed, since the S.S. Arcadia‘s manifest can be seen to have two Allosaurus on it: one which is said to be a juvenile and one which, like the other adult dinosaurs, is not. According to members of the Universal Studios design team, the allosaurs appearing in Jurassic World: Fallen Kingdom were the male design, with a separate female design not appearing in the film.

The body of the allosaur designs used in the films was allegedly based on the common species Allosaurus fragilis, but the skull anatomy was based on Allosaurus jimmadseni (which was, at the time, classified as A. fragilis). Because the skull anatomy is the primary means of differentiating these two species, Jurassic-Pedia has chosen to classify the species appearing in the films as A. jimmadseni.

Director Colin Trevorrow has stated that the Allosaurus which appears in the 2019 short film Battle at Big Rock is a female, and is the matured form of one of the juvenile allosaurs which escaped the Lockwood estate at the end of Jurassic World: Fallen Kingdom. Its design was noticeably changed, making it appear different from the established appearance of adult allosaurs shown in Jurassic World: Evolution in 2018. The allosaur in the Jurassic World motion comic is depicted with the design of the males from Jurassic World: Fallen Kingdom; it also lacks the blind right eye of the one seen in the short film. The 2021 game Jurassic World: Evolution 2 interprets this as being a pair of allosaurs, rather than the original explanation (that the motion comic, with its lax oversight, had made an illustrating error).

Notable Individuals

Auctioned Allosaurus – male individual sold as a subadult on the black market in 2018

Female Allosaurus – Big Rock National Park – female individual transplanted to the Pacific Northwest

Disambiguation Links

Allosaurus sp. (L/M)

Allosaurus fragilis (IDW-DG)

Allosaurus fragilis (IDW-JPR)