Herrerasaurus ischigualastensis (S/F) / (S/F-T/G)

Herrerasaurus-logoAmong the earliest known dinosaurs, Herrerasaurus (meaning “Herrera’s reptile from Ischigualasto”) was discovered in 1959 near San Juan, Argentina by a goatherd named Victorino Herrera, and was described by paleontologist Osvaldo Reig in 1963. Herrerasaurus lived about 231 million years ago, during the Ladinian epoch of the Middle Triassic. Herrerasaurus was found in the Ischigualasto Formation, particularly Ischigualasto Provincial Park (sometimes called Valley of the Moon). Fossils have not been found anywhere else. Two other dinosaurs from this formation, Ischisaurus cattoi and Frenguellisaurus ischigualastensis, are now believed to be subadult Herrerasaurus.

While initially described as a primitive carnosaur, the classification of Herrerasaurus was hotly debated for three decades after its discovery. It was classified variously as a prosauropod, an unidentifiable saurischian, an extremely basal dinosaur, and even a non-dinosaurian reptile.

A team led by paleontologist Paul Sereno discovered a complete Herrerasaurus skull in 1988, leading to the development of two schools of thought on its classification. Some authors consider it to be a basal saurischian, existing before the most recent common ancestor of theropods and sauropods. Other authors, including Sereno himself, consider it (and the family to which it belongs, Herrerasauridae) to be a basal theropod.

As of the 1993 Isla Nublar incident, International Genetic Technologies had obtained enough Herrerasaurus DNA from ancient amber samples to clone the species. Its viability as of the incident was listed as 60%; despite this, four animals were successfully cloned. This allowed InGen scientists to determine that, based on the anatomy of the cloned specimens, Herrerasaurus was indeed a basal theropod.


This dinosaur measured 3 to 6 m. (9.8 to 19.6 ft.) in length, at least 1.1 m. (3.6 ft.) tall, and weighed from 210-350 kg. (463-771.6 lbs.). No adults existed as of the 1993 incident, but InGen scientists estimated a maximum length of 20 feet for these animals; this matches up with the maximum size estimated by paleontologists. In the cloned specimens, about a third of the animal’s length consists of its partially-stiffened tail, which is used for balance while both running and climbing. The tail’s vertebrae overlap, which reduces its flexibility. The characteristically low-slung body gives this dinosaur a markedly different profile from later theropods, which would typically keep the head raised higher; in Herrerasaurus, the head and neck are kept mostly parallel to the ground.

As with InGen’s more advanced theropods, the hands on Herrerasaurus are pronated, meaning the palms may face downward, unlike in fossils. Both the hands and feet possess five digits, three of which terminate in sharp, curved claws. The clawed fingers and toes are designed for grasping; they permit this dinosaur to easily cling to structures and presumably prey items as well. Only the middle three toes bear weight, and the fifth toe (the innermost) lacks a claw. On the hands, only the first two fingers and the thumb have claws, while the others are highly reduced and have no claws. The legs in particular are very muscular and designed for endurance, with short thighs and long feet; the arms are half the length of the legs, and the hands (much like the feet) are elongated. The mobile application Jurassic World Facts estimates its running speed at around 23 miles per hour.

The head of this dinosaur is small, especially when compared to the enlarged skull size of the ecologically similar Velociraptor or the massive bite force of the Tyrannosaurus. It reaches 56 cm. (22 in.) in length when fully grown; the juveniles involved in the 1993 incident were around half this size. The skull lacks significant ornamentation such as crests or horns, more closely resembling the skulls of more primitive archosaurs which existed before the dinosaurs. On its lower jaw is an unusual flexible joint which allows it to slide back and forth, allowing for a grasping bite. This is not known in other dinosaurs, but is a feature in the jaws of some lizards. The teeth are large, though variable in size, and serrated to tear off chunks of flesh from prey. Its eyes are birdlike, with round pupils and yellow sclerae. The head is poised on the end of a strong, flexible neck. Herrerasaurus has a lengthy triangular tongue. Both its tongue and the interior of its mouth are pale blue in color. Its digestive system overall is highly robust, capable of digesting bone; this means its stomach pH is comparable to that of the bearded vulture (Gypaetus barbatus), which has a stomach pH of slightly above zero.

The scaly skin of this dinosaur is remarkably vibrant. Its body is a crimson red or orange, patterned with wavy black, gray, or brown striping from snout to tail. On the middle of the back, its red or orange colors may fade to yellow. As with many dinosaurs, it exhibits countershading, with the underside being much lighter than the back. Countershading on Herrerasaurus is particularly vivid, with a distinct stripe of creamy white on the ventral side contrasting with the bright decorative patterning of the dorsal side.


Only the juvenile stage of Herrerasaurus has been observed. These animals were approximately half the size of fully-grown adults, which are projected to reach twenty feet in length. It is not known if the adults would undergo any changes in physical appearance as they reached full size, or if the juveniles simply resemble smaller versions of the adults.

Sexual Dimorphism
The grasping hands of Herrerasaurus are not only suitable for grappling with prey, but also assist in climbing. Its feet can be used in a similar fashion.

Due to a lack of specimens observed, sexual dimorphism in Herrerasaurus is not known. The sexes of the four juveniles involved with the 1993 incident are not known; they are presumed to be female, but due to the likely inclusion of genes from Hyperolius viridiflavus coding for protogyny, it is possible that some may have been males.

Preferred Habitat

The environmental preferences of Herrerasaurus are mostly unknown. Four juveniles were bred with the intention to house them in what was once the Velociraptor paddock, suggesting that these two genera have similar habitat requirements. Four juvenile Herrerasaurus, once freed from captivity, migrated to an area with a large cliff and complex artificial structure, suggesting that they prefer dynamic environments where they can climb. Also present in that area was a large waterfall, indicating a preference for sources of running water nearby.

In real life, the area which Herrerasaurus inhabited was a volcanically active floodplain with a wet, warm, and heavily forested environment which experienced seasonally heavy rainfall.

Muertes Archipelago

InGen originally bred Herrerasaurus on Isla Sorna, though population statistics remain unknown; data implies that the first ones would have hatched in late 1992 or early 1993. The species was not listed among the island’s species as of the time InGen abandoned the island, so it was most likely no longer on Isla Sorna as of 1993. Four juveniles would have existed on the island as of spring or early summer that year, but were shipped to Isla Nublar before the incident.

While it is not film-canon, the game LEGO Jurassic World does display a Herrerasaurus icon on a map of Isla Sorna. The icon appears in the southeast region of the island, northeast of the Workers’ Village. This game uses an older version of the Isla Sorna map, which places the Workers’ Village near the southeastern coast rather than the central island as in the final film; this leaves the intended placement of the herrerasaur habitat ambiguous. In either case, InGen documentation heavily suggests that no herrerasaurs remained on the island by the time it was abandoned.

If any herrerasaurs were on Isla Sorna as of 2004, they would have been collected by InGen (now under the banner of Masrani Global Corporation) and brought to Isla Nublar.

Isla Nublar

Sometime before June 1993, four juvenile Herrerasaurus were introduced to Isla Nublar and were maintained in a holding pen in the central island. Their age implies that they would have hatched relatively recently, but the exact date is not known. InGen intended to ultimately house them in what had previously been Jurassic Park‘s Velociraptor paddock, located at the northern end of the Jungle River in a heavily forested region.

Known (red) and planned (orange) range for H. ischigualastensis on Isla Nublar, as of June 11, 1993

On June 11, 1993, the power was cut to Park security systems by a disgruntled employee. As a result, the herrerasaurs were able to escape confinement. The four juveniles appeared to remain together after leaving their holding pen, exploring the surrounding area; on the evening of June 12, all four were witnessed at the construction site of the Bone Shaker rollercoaster. This was not extremely far away from the holding pen, suggesting that the animals keep to a relatively limited territory at this age.

Footprints found on the western mountain ridge on the evening of June 12 likely belonged to at least one of the juvenile Herrerasaurus; they are medium-sized three-toed tracks, meaning that they cannot come from Velociraptor or Troodon. Too large to be Compsognathus and too small to be Tyrannosaurus, they do not match up with confirmed Dilophosaurus prints; Herrerasaurus was the only other nonavian theropod on the island at the time, and therefore the one which made the prints. This environment is heavily forested and features a large cliff face, similar to the one near the Bone Shaker where the animals appear to have ultimately set up territory.

Known (red) and hypothetical (purple) range of H. ischigualastensis on Isla Nublar between June 11, 1993 and June 12, 1993

During the incident, all four Herrerasaurus died due to injuries sustained during a hunt on June 12. This would mean the extinction of this species on Isla Nublar.

Two juvenile Herrerasaurus track prey items, Isla Nublar (6/12/1993)

If any Herrerasaurus survived on Isla Sorna, they would have been transported to Isla Nublar between late September of 2004 and May 30, 2005 when Jurassic World opened. After some time in the quarantine paddock, the herrerasaurs would be integrated into habitats in Sector 5. Population statistics remain unknown; it is not even known if any herrerasaurs existed on Isla Nublar during this period of time at all. A report released on February 4, 2018 by the Dinosaur Protection Group listed Herrerasaurus among the species which were suspected of having become extinct due to neglect and poor treatment by humans.

Mantah Corp Island

In the 2000s and early 2010s, InGen rival Mantah Corporation illegally appropriated de-extinct animal specimens and exploited them in a facility which operated on Mantah Corp Island. However, no evidence currently suggests that Herrerasaurus was among the animals cloned there.

Biosyn Genetics Sanctuary

In the early 2020s, Biosyn Genetics was authorized to collect de-extinct animal specimens from the wild and securely house them at specialized facilities. The largest of these was the Biosyn Genetics Sanctuary in Italy. Since Herrerasaurus was practically extinct during that period of time, it was not housed there.

After the incident of late 2022, Biosyn Valley and its sanctuary have been overseen by the United Nations. If any Herrerasaurus are sent here in the future, they will be guarded by the UN along with what remains of Biosyn.

Black market

If any had been created during the following twenty-two years, is is possible that they may have been subject to poaching; there is currently no information available about which species are suspected to have been poached from the Muertes Archipelago or Isla Nublar prior to 2018.

Herrerasaurus DNA could have entered the international black market after 2018. This means that interested parties could potentially clone this animal. If this comes to pass, it will likely end up being trafficked through major black market hubs such as the Amber Clave which operates in Valletta, Malta. A single specimen was supposedly photographed in late May somewhere in North America, suggesting that someone somewhere has bred Herrerasaurus back to life; keeping it contained is another matter, and a task at which the mystery breeder has apparently failed.

Wild populations

Among the earliest-known dinosaurs, Herrerasaurus existed about 231 million years ago in southern Pangaea. It inhabited floodplains on the western side of the Gondwanan subcontinent, what is now South America. This environment included abundant rivers controlled by seasonal heavy rainfall, and was volcanically active. As far as fossil remains inform, this dinosaur existed for only a short time before the changing environment caused it to become extinct. This was one of the most ancient animals to be brought back from extinction by geneticists during the late twentieth century, having been gone since the mid-Triassic period.

A single intriguing photograph reported to the Department of Prehistoric Wildlife on May 29 (apparently taken the day before) shows what appears to be a Herrerasaurus in a temperate forested region. The photographer’s location was not given, but since he was a native English-speaker it was probably the United States or Canada. No record of Herrerasaurus was present in DPW records, nor was the animal advertised by Jurassic World, leading to both experts and amateurs struggling to identify the animal.

Behavior and Ecology
Activity Patterns

Fossil evidence suggests that the Herrerasaurus was originally a cathermal animal during the Triassic, active for intervals throughout the day while resting in between. This animal has been observed engaging in patrolling and hunting behaviors in the late evening, close to twilight.

Diet and Feeding Behavior

Dr. Laura Sorkin‘s research characterizes Herrerasaurus as a pursuit hunter. Like many more advanced theropods, the herrerasaur may hunt in packs, at least as a juvenile; typically patrolling their territory in pairs, they will vocalize to one another upon sighting a prey item and engage in the chase cooperatively. Though they are not highly intelligent, herrerasaurs are able to use some rudimentary strategizing and coordinate with their packmates during a hunt. According to Dr. Sorkin’s observations, a herrerasaur can be quite a determined hunter and unlikely to give up easily once it has targeted a prey item. This suggests that they will try to tire out their prey through a lengthy chase, making the kill once the prey is too exhausted to continue running.

Herrerasaurus makes a leap for a prey item, Isla Nublar (6/12/1993)

The claws on both its hands and feet are curved, and the limbs are powerful for grasping prey items. Its jaw is also designed to give a gripping bite; it has a large number of sizable serrated teeth which it uses to rip and tear pieces of meat off of its prey. In Jurassic World: Evolution, it also uses the claws of its hands to tear meat off of food items. The mobile application Jurassic World Facts states that the prey of this animal includes small dinosaurs, reptiles, and mammals; the species Pisanosaurus is given as an example of a prey item. However, this species has never been cloned by InGen, so the specimens in Jurassic Park would not have been able to hunt it.

Herrerasaurus is an incredibly efficient predator. In addition to tearing off chunks of meat from prey and swallowing them whole, it is able to digest bone; this is a feat that would give the herrerasaur an edge over competing predators, even Tyrannosaurus.

Social Behavior

Despite its lower intelligence, Herrerasaurus is a social animal (at least in the juvenile stage). Only four animals are known to have been cloned, but all four remained close together even after having been released from containment. Establishing a territory at the Bone Shaker, they paired off to patrol separate parts of it. This pairing-off behavior appears to extend to hunting; when targeting prey items, only two at a time participated in the attack. If one animal failed, another would take its place.

Two juvenile Herrerasaurus cooperating to surround prey. Herrerasaurus is known to often work in pairs when patrolling or hunting.

The vibrant coloration of Herrerasaurus is also indicative of social behavior, as these bright colors and patterns would make species recognition quick and simple. As the four animals created by InGen were physically-identical clones, it is not currently known if there is any level of individualism in the patterning of each herrerasaur.

It is not known if the same two animals always pair off together and favor each other as companions, or if they simply operate in pairs to increase their efficiency. In the game Jurassic World: Evolution 2, social interactions between Herrerasaurus are a little more detailed, including more primitive forms of the social interactions seen in later theropods. Craniofacial biting and shoving matches are common forms of non-aggressive competitive behaviors that help these animals hone their strength and skill while also serving as ways to establish dominance among each other.


As with all dinosaurs, Herrerasaurus hatches from eggs and has a cloaca. The eggs of theropods are ovoid, like those of modern birds. InGen scientists believe that this egg shape helps to keep the eggs from rolling away from where the parents placed them. Since Herrerasaurus is a primitive theropod, it may have already possessed this evolutionary trait.

Small to medium dinosaur eggs typically incubate for three to six months, with smaller dinosaurs having shorter incubation periods. The largest dinosaur clutches contain twenty-one eggs; most have fewer than this, and Herrerasaurus likely lays eggs in numbers similar to other theropods in its size range such as Dilophosaurus.


Jurassic Park: The Game portrays herrerasaurs as making cries very similar to those of Velociraptor; the herrerasaur vocalizations are simply slowed-down raptor vocalizations. It is not known if this is intended to represent the actual sounds that this dinosaur makes in the film canon, or if it was simply done due to a lack of resources needed to create new sounds.

The animals vocalize frequently when pursuing prey, most likely to coordinate with one another.

According to the Jurassic World Facts app, this animal communicates with other members of its own kind using trilling noises. In Jurassic World: Evolution, it can be heard making hissing and rattling noises to communicate.

Ecological Interactions

Because the four known Herrerasaurus were only in the wild for one day at most before dying, little is known about their role in local ecology. As predators, they would regulate the populations of smaller prey items including reptiles and mammals.

The territory established by the four escaped herrerasaurs on Isla Nublar was not known to be inhabited by other animals at the time, but there is evidence that one herrerasaur did pass through a region of the western mountain range which was inhabited by other theropods. These included Compsognathus, Dilophosaurus, Troodon, and Tyrannosaurus. It is possible that Pteranodon may have been in the same area, as well as flocks of Franklin’s gulls (Leucophaeus pipixcan). The gulls are potential food items, as are the compies, but the other medium-sized theropods would likely be competition and the Tyrannosaurus would be a potential predator of the herrerasaurs.

As the herrerasaurs are able to digest bone, they would be one of the ecosystem’s most efficient scavengers. Clearing away carcasses would eliminate a potential source of disease, and as they eat everything including the bones, they would maximize the return of nutrients into the food web.

Herrerasaurus was possibly affected by hematophagous (blood-drinking) parasites, at least in its native Triassic period. Mosquitoes had not yet evolved, so these parasites would have to belong to a different group of animals (possibly early relatives of ticks). It is not known if any modern parasites consume their blood. Their ability to digest bone means that they must have a stomach pH so low as to kill virtually all microorganisms they consume along with their food, meaning that Herrerasaurus is unlikely to contract food-borne illnesses.

In Jurassic World: Evolution, they are susceptible to the bacterium Campylobacter, which is very common in modern poultry. Similar to extant birds, this primitive theropod can become diseased with campylobacteriosis due to this bacterium.

Cultural Significance

Herrerasaurus is probably one of the best-known Triassic dinosaurs and is commonly seen in dinosaur encyclopedias as an example of one of the earliest dinosaur species. It is not as famous as other species which evolved later, but is a decently popular creature among more serious dinosaur enthusiasts and is a common staple in paleoart.

Its genus is named for goatherd Victorino Herrera, who discovered its remains.

In Captivity

Not much is currently known about how Herrerasaurus fares in captivity. It was intended to be housed in what was originally Jurassic Park‘s Velociraptor paddock, a forested area on the Jungle River notable for its huge Moreton Bay figs. Four juveniles were bred as of June 1993 and were kept in a holding pen for eventual transport to their habitat, but never made it there; they escaped captivity during the 1993 incident.

Some information about their preferred habitat, and therefore what they would need to thrive in captivity, can be gathered from the territory they chose after escaping. They settled at the Bone Shaker, an unfinished roller coaster attraction set on the side of a cliff near a large waterfall. This suggests that Herrerasaurus prefers dynamic, structured environments with places it can climb and a source of running water nearby. It was observed engaging in cooperative hunting, so social structure is important at least for juveniles. Although it is not a smart theropod, collective intelligence and an ability to scale most walls makes it an escape risk.

In terms of feeding, not much is known other than Herrerasaurus can digest virtually any animal matter. It is probably one of the easiest carnivores to feed since it can digest meat and bones alike. This ability could only come from a highly acidic stomach pH, meaning it would have little to worry about food-borne pathogens since it would kill most microorganisms it consumed. The carcasses of dead animals could be fed to Herrerasaurus with ease.

Excerpt from Dr. Laura Sorkin’s field journal. Herein she describes the hunting behavior of H. ischigualastensis.

InGen intended Herrerasaurus to be used as a “safe” replacement for Velociraptor in Jurassic Park, and it would have inhabited the paddock originally intended for the raptors. Visitors would have therefore viewed them from the Jungle River Cruise attraction. The InGen Field Guide suggests that Herrerasaurus could also be showcased in special exhibit pens where visitors could interact even more closely with them, probably as a part of the Jungle River Cruise. Their efficiency at scavenging would also make them ecologically useful to the Park. However, some InGen staff (including Robert Muldoon and Dr. Laura Sorkin) expressed safety concerns about the animals.

During the Board‘s review of Jurassic Park in early June 1993, the location of the herrerasaur holding pen was brought up by Robert Muldoon as a security concern. Its proximity to the Bone Shaker was given as a possible danger; however, the Board considered current safety measures to be satisfactory. Ignoring Muldoon’s concerns proved unwise, as during the 1993 incident the herrerasaurs were able to access areas used by humans fairly easily.


Among the earliest-known dinosaurs, Herrerasaurus has been extensively studied by paleontologists in an effort to determine its classification and evolutionary relationships. It was variously considered to be a primitive theropod, an early relative of the sauropods, a saurischian of uncertain affinity, a basal dinosaur existing outside the major taxonomic groups, or even a non-dinosaurian reptile. Many paleontologists agree with the “primitive theropod” conclusion, which is also supported by InGen research.

It is notable in the Genetic Age for being the oldest species at the time added to InGen’s genetic library, and the oldest dinosaur to have been made de-extinct (and then re-extinct, and then possibly de-extinct a second time). While living specimens would have given fascinating looks into the behaviors of early theropod dinosaurs, potentially revolutionizing our understanding of how these successful animals got their start, very little was learned about them before they died. What was learned was that active hunting and dynamic social behavior appear to be some of the oldest theropod behavioral traits.


Since it almost certainly became extinct in 1993, Herrerasaurus has little significance to the de-extinction debates. It was included in a list of Isla Nublar’s de-extinct animal species by the Dinosaur Protection Group; it is listed in red like the confirmed extinct species, implying that it is indeed still extinct. The loss of these species was cited as an act of cruelty by the DPG. A single specimen photographed in May 2022 by a hiker suggests that it may have been cloned again, but it seems to be incredibly rare.


InGen meant for this dinosaur to be an attraction in Jurassic Park, and this was one of the final additions made before the 1993 incident halted development. Previously, the main small theropod was planned to be the intelligent and exciting Velociraptor, but this dromaeosaur proved too much of a challenge and was phased out of the Park roster. The herrerasaurs were approved as a safer alternative, since their lower intelligence was believed to make them less of a hazard. InGen planned to show them at attractions where visitors could see them up close, capitalizing on their beautiful colors to draw crowds. Unfortunately, Jurassic Park was never completed, and the deaths of all four Herrerasaurus meant they would never see the light of day as a de-extinction exhibit. Just how successful they would have been might never be known.

In addition to its unrealized potential as a park attraction, Herrerasaurus would have had potential biomedical applications as a source of biopharmaceutical compounds. The original animal’s exact biochemistry has not been seen in over 230 million years, a version of it would have been resurrected through genetic engineering in the 1990s. Unfortunately its applications here are also not explored.

A Herrerasaurus skull was among the fossils and models in Benjamin Lockwood‘s possession; while it is possible that the skull may have been from one of those cloned by InGen in the 1990s, it is equally possible that it was a fossilized specimen.


Although this dinosaur is exceedingly rare, there is technically nothing preventing more of them from being cloned, and their ability to climb walls and cliffs might allow them to escape into the wild. In fact, there is some evidence it may have already happened. Many of the same self-defense techniques you would use against other small theropods will work here, though an adult Herrerasaurus can reach twenty feet in length and might be hard to intimidate.

The unique threat of Herrerasaurus is its sheer determination. With most theropods, you can escape them either by getting out of their territory, hiding, or driving them away. Herrerasaurus is far harder to best. It is a determined hunter, unwilling to give up the chase; this is actually its main strategy. It tires out prey through extended pursuit, making the kill once its victim is too exhausted to run any longer. Unless you can get reliably out of reach, just running away from it is unlikely to help you; it will continue to follow at a distance, figuring out ways over any obstacles between you and it. Effective barriers that it cannot scale are mostly technological in nature, such as electrified fences. If vehicles or buildings are available, you might take shelter, but avoid hiding places with windows or doors that can be easily broken down. Do not leave your hiding place until greater help has arrived to aid you, since the dinosaur is likely to be patiently waiting for you to let your guard down.

If you must face it in direct combat, remember the usual vulnerabilities of dinosaurs: their scaly skin provides some defense, but their eyes, nostrils, ears, and mouths are vulnerable. Using any weapons you have at your disposal, strike at the head. It will try to grapple with you, immobilizing you so that it can bite down. Try to block its jaws with a sturdy object. You may also want to wear thick, protective clothing if you expect to encounter this or any other small theropod, since this will reduce the damage you take from bites and lacerations. These dinosaurs usually hunt in pairs or small groups, so they are unlikely to be alone. You should not be either: always travel with companions who can help keep an eye out for danger and defend each other against threats.

So far, only one human-herrerasaur conflict has been reported and resolved, but it ended with the deaths of all four dinosaurs. Jurassic-Pedia does not condone violence against animals, but we do acknowledge that any living thing must defend itself by whatever means necessary.

Behind the Scenes

The scene in Jurassic Park: The Game which features the herrerasaurs is a tribute to their original discovery in Argentina. Fossils of Herrerasaurus were found near a cliffside goat-herding path, and the Bone Shaker was said to have been built over an ancient goat-herding path and is located on the edge of a cliff.

Although this dinosaur was never to appear in any of the films, it was acknowledged by viral media associated with the Jurassic World trilogy. It appeared physically in a photograph created by a fan for the Dinotracker social media campaign, which the fictional Department of Prehistoric Wildlife claimed to be unable to identify. They commented on the photo “Our bones are shaking!” in reference to the Bone Shaker scene in Jurassic Park: The Game.

Notable Individuals

Juvenile Herrerasaurus – four individuals bred for Jurassic Park; deceased in 1993