Mosasaurus maximus (S/F)

mosasaurus-detail-headerMosasaurus maximus is an extremely large species of marine mosasaur. Its genus name means “Meuse River lizard,” referring to the place in the Netherlands where its genus was first found. This reptile was discovered by Johan Leonard Hoffman and formally given a full scientific name by William Mantell in 1829. This species lived during the late Cretaceous period from 70 to 66 million years ago. Mosasaurus belongs to the family Mosasauridae, and its bones have been recovered from all continents that once bordered the Atlantic Ocean. This particular species, M. maximus, was found in the Fox Hills Formation, which stretches from Alberta to Colorado. Its specific epithet “maximus” refers to its size, as it is the largest species of Mosasaurus.

There are several species of Mosasaurus known. The type species (and largest known in real life) is M. hoffmanni, a fifty-six-foot reptile with which M. maximus is typically considered synonymous. In the Jurassic film franchise, scientists determine that Mosasaurus maximus is its own distinct species, instead of being the same as M. hoffmanni, thus making M. maximus the largest known species instead. Other species include M. conodon, M. lemonnieri, M. beaugei, and M. missouriensis.

On August 25, 2000, InGen’s Dr. Henry Wu reported that researchers Bridges and Curtis, et al. at their San Diego location had utilized a prototype of a new iron analyzer to discover traceable DNA fragments in a recently-discovered fossil mosasaur skeleton. With this new technique, InGen was able to reliably clone marine animals; until the invention of the iron analyzer, a lack of amber samples containing parasites which had fed on marine life would make the DNA of these animals an extreme rarity. After this animal was cloned in 2006 or 2007, the immense size that it grew to led InGen researchers to conclude that it was Mosasaurus maximus, according to a statement made on March 20, 2015 by Dr. Brian Switek.


The most striking feature of M. maximus is, of course, its size. Most infographics in Jurassic World’s attractions stated that it reaches lengths of fifty-five feet, which is consistent with paleontological knowledge. However, even a passing glance at the specimen from the park reveals that it is noticeably larger. The Jurassic World website and a May 2015 article by Dr. Brian Switek state that the animal is sixty feet long, which would make it slightly larger than known specimens. The Jurassic World Facts mobile application gives it a length of 71.8 feet long. The books The Park is Open and Jurassic World: Where Dinosaurs Come to Life, which released in May 2015, list the mosasaur’s length as 72 feet (The Park is Open is more precise, at 72.2 feet). The mosasaur appears to continue growing throughout its life, as a June 8, 2018 social media post by the Dinosaur Protection Group lists its length at 84.9 feet and a weight of 30 tons. (A 2019 social media infographic released by Universal Studios lists 21.9 meters, or 71.9 feet.) However, its size in 2018 appears to have increased immensely, reaching around 120 feet. Weight estimates have also varied; Jurassic World social media has listed it at 28 or 29 tons, while the official website listed it at both 15 tons and 5 tons at different places on the site. As five tons is an extreme low outlier in the weight estimates, it is most likely an error on the part of the website. The DPG has given a 30-ton weight estimate as of June 8, 2018; as the mosasaur has grown enormously larger than any of the given lengths, it is likely heavier than any of these estimates as of 2018 as well.

A post from Jurassic World social media giving one of several weight and length estimates for the Mosasaurus.

Notably, the 70- to 80-foot lengths this animal reached when in captivity would already make it the largest carnivorous vertebrate ever known, though some planktivorous whales such as the blue whale were still larger. It was also exceeded in length by some of the largest sauropod dinosaurs. When in the wild, the maximum known size is closer to 120 feet, meaning it is longer than all known animals except for the longest-recorded lion’s mane jelly (Cyanea capillata), which also reached 120 feet long including the tentacles, and possibly the bootlace worm (Lineus longissimus), which has been reported at 180 feet long when stretched out.

The second most noticeable feature of the mosasaur is its enormous mouth, lined with 88 sharp, cone-shaped teeth. Its upper palate has a secondary row of teeth, called the pterygoid teeth, which assist it in handling live prey. The mouth is capable of opening very wide, and when biting down, exerts 13,000 pounds of force. This exceeds the bite force of Tyrannosaurus rex. Its muscular tongue is comparatively short; it is thick and pointed rather than forked, and is pink in color. The mosasaur’s nostrils are located about halfway down its snout, on the dorsal surface rather than the front or sides. This would mean it breathes at the surface similarly to a whale. The skull itself is very long, consisting mostly of the jaws, and tapers to a rounded point. Its eyes have yellow sclerae and round, black pupils.

Left eye of an adult female Mosasaurus reacting to light stimulus

Instead of feet, all mosasaurs have four paddle-like flippers which are too small to use for propulsion. They are utilized for steering, and the front flippers have some limited use when the animal rests on a solid surface. It is unable to walk or crawl on land due to its enormous bulk and lack of muscular limbs, but its front flippers can help it maintain stability and shift the front half of its body left and right.

Because it inhabits salt water, the mosasaur must have salt glands for osmoregulation. In birds and reptiles, salt glands are located in or on the head, generally near the eyes, nostrils, or mouth. In the only modern marine lizard, the marine iguana Amblyrhynchus cristatus, excess salt is expelled through the nostrils, so this is most likely the case in Mosasaurus as well.

Its long, tapering body is protected by scaly skin, including several rows of particularly large and thick scales on its dorsal side. These give the appearance of osteoderms similar to those of crocodilians, a feature not known in mosasaurs or their relatives. Most of its body scales are keeled, which allow it to cruise through the water more smoothly; this allows it to ambush prey without alerting them by its wake. In addition, a row of tall triangular scales runs down the dorsal side all the way to the tail. Like most marine animals, it exhibits countershading, with a darker blue-gray color on the dorsal side and lighter on the underside.

The lengthy, powerful tail of the Mosasaurus is used for propulsion through the water, while the flippers assist in steering.

The body of this mosasaur terminates in a lengthy tail with a large hypocercal caudal fin. This means that the vertebrae extend into the lower lobe of the fin, making the lower lobe larger. In the case of the only known cloned Mosasaurus, the upper lobe is so much smaller than the lower lobe that it can be missed at a cursory glance. The mosasaur’s caudal fin is often called a “fluke,” like the tail of a whale; however, the mosasaur’s tail fin is anatomically very different from a whale’s, and has more in common with the tails of certain fish. Powerful strokes of the tail are used to propel the mosasaur through the water.


Only the adult stage of the Mosasaurus maximus has been observed directly, but a LEGO version of the infant makes an appearance in the animated series Legend of Isla Nublar. It is depicted as essentially a smaller version of the adult, with the fins and head proportionally larger and with noticeable dark stripes which are highly faded in the adult. Its body color is overall darker in this depiction of the infant stage.

While this animal’s natural growth rate is unconfirmed, the female bred in 2006/2007 reached its original projected length by 2014. It is not known if it was given any kind of growth-boosting supplements. Between December 2015 and June 2016, its listed length increased by 12.7 feet; if these measurements are accurate, its growth rate for that period of time was 2.12 feet per month. After it was reported missing, its size increased to 120 feet. If it attained this size between June 2016 and June 2018, this would mean it grew 35.1 feet in the intervening two years. This would put its growth rate for that time at 17.55 feet per year, or 1.46 feet per month.

Sexual Dimorphism

Only the female Mosasaurus has been cloned. Thus, any sexual dimorphism remains unknown.

Preferred Habitat
Detail on the mosasaur’s mouth as it prepares to consume prey. Note the tongue and pterygoid teeth.

This reptile inhabits nearshore marine environments, though its bulk requires it to maintain some distance from intertidal zones. If it is to approach land, it must have an immediate steep drop-off so that it does not become stranded. As most of its prey inhabits surface waters, this animal does not dive terribly deep. While it was bred in tropical waters, its size makes it gigantothermic, so its sheer bulk would protect it from colder temperatures. It has been known to inhabit waters where the lower temperature range is around 34 degrees Fahrenheit (in the Bering Sea), but the actual extent of its cold tolerance is not currently known. At adult size, it requires a habitat containing about three million gallons of salt water. To prevent waste accumulation, this water must be circulated out, necessitating a large outflow system (Jurassic World used a partially overland and partially underground canal system to accomplish this).

The mosasaur’s original habitat, like that of most de-extinct species, was vastly different from the environment it must inhabit today. As a result, Dr. Henry Wu had to alter certain genes to allow its survival in the modern world, as with many other animals. As of late August 2004, he was working on acclimatizing the genome to the waters of Isla Nublar, but the exact nature of the modifications made remains undisclosed.

Mosasaurus maximus is seasonally migratory and constantly moves around the ocean in search of adequate food sources. Between June 2016 and sometime following June 2018, the only known mosasaur had traveled from Isla Nublar to O’ahu (4,798 miles northwest); by 2019, it was sighted off the coast of New Zealand (4,000 to 5,000 miles southwest of O’ahu). This, however, is far from the longest distance traveled by a marine reptile: a leatherback sea turtle (Dermochelys coriacea) was recorded traveling over 12,000 miles (19,312 kilometers) in 647 days, and females of this species regularly make journeys of 6,000 miles (9,656 kilometers) or more when traveling from feeding grounds to nesting grounds. Mosasaurus maximus appears to travel shorter distances in the same amount of time, likely expending more energy in active hunts than in long-distance travel.

Muertes Archipelago

Although it has not been privately bred there, the Muertes Archipelago is easily within the migratory range of Mosasaurus within the Pacific Ocean.

Isla Nublar

A single female Mosasaurus maximus was bred on Isla Nublar for exhibition in Jurassic World. It was stated to be 11 years old as of May 15, 2018, meaning it was bred sometime between May 16, 2006 and May 15, 2007. It was placed in the Jurassic World Lagoon, where it was kept on exhibit until the park closed on December 22, 2015. During this time, it was restricted in its movements by security systems in place in the Lagoon. It was kept in the Lagoon’s western half, unable to move into the shallower eastern half due to a security fence bordering the monorail track. If need be, it could be restricted from the area nearest Main Street by a secondary fence, but this was not usually in place during normal park operations. It is known to have been raised at some point shortly following the 2015 incident, as it was still in the raised position in 2018.

After the park was shut down, the security systems in place around the Lagoon began to break down due to neglect and the harsh weather of the Central American wet season. Within six months, the monorail and fencing system in the Lagoon had suffered serious damage; once the fence had been broken enough, the mosasaur would have had access to both halves of the Lagoon. Due to its huge size, it could potentially have sped up the destruction of these artificial barriers using its strength.

At an unknown date in June 2016, human interference allowed the mosasaur into the canal system that fed the lagoon, from which point the mosasaur escaped via the island’s waterways into the surrounding ocean. After this it began migrating around the Pacific, though it may sometimes pass near Isla Nublar.

Mantah Corp Island

In June 2016, the only specimen of Mosasaurus was reported near a kelp bed off the western coast of Mantah Corp Island, and has possibly visited the vicinity in the following years. However, it has not been intentionally kept at the island facility by its owners.

BioSyn Genetics Sanctuary

De-extinct animals were captured by BioSyn Genetics and housed in facilities such as the BioSyn Genetics Sanctuary from the early 2020s onward. However, without a massive marine environment there, the Mosasaurus could not be housed and is instead allowed to live in the wild while being tracked by the Department of Prehistoric Wildlife.

Black market

DNA from this species, as well as numerous other de-extinct organisms, entered the international black market in mid-2018 and has been acquired by both governmental and non-governmental entities. A major hub of genetic trade is the Amber Clave, a notorious night market in Valletta, Malta. The original Mosasaurus specimen itself is probably too large to be captured by most private entities and remains in the wild.

Wild populations

The first species of Mosasaurus evolved about 82 million years ago, though M. maximus itself was one of the later species to appear around 70 million years ago. This particular species inhabited what is now the Caribbean Sea, including what was left of the Western Interior Seaway at the time. Other species of Mosasaurus lived all throughout the Atlantic Ocean from North America to the islands that would eventually become Europe, and as far south as Antarctica. Some have even been found in western Asia, which at the time was not geographically connected with Europe. This was a common, very successful genus of reptile. It became extinct as a part of a mass extinction event roughly 66 million years ago, along with most of the large marine animals alive at the time. Millions of years later, geneticists succeeded in cloning a single Mosasaurus maximus in the early twenty-first century.

Following its escape from Isla Nublar in June 2016, the Mosasaurus traveled a short distance eastward and was seen near Mantah Corp Island; the next time it was seen was two years later, near the North Shore of O’ahu, Hawaii in mid-June 2018. Within the next year, it was sighted near New Zealand. By 2022, a regular migratory route around the Pacific Ocean had been observed: this route begins off the Central American coast before moving into deeper water, crossing the sea to Hawaii. Hanalei Bay, Kauai is known for sightings. After this, its migration takes it toward North America, sometimes appearing near Alcatraz Island, Cape Perpetua, and Seattle, Washington. Then it heads farther north into colder waters, frequenting the Bering Sea where it has made a habit of stealing from fishing vessels. Sightings have been reported near Kathryn’s Hook, Alaska. Following the curve of the Aleutian Islands, the mosasaur eventually nears Japan, where it has been sighted near Okinawa. Then it continues south, arriving near Auckland, New Zealand. Crossing the southern Pacific, its migratory route then begins for a new season.

Behavior and Ecology
Activity Patterns

The mosasaur is primarily diurnal, but is known to be active during both the day and night. The behavior of the individual in Jurassic World was heavily influenced by the park’s schedule, as it was given food every two hours during the park’s operation; as the park was open from 8:00 AM to 10:00 PM, and the first scheduled mosasaur feeding at 9:00 AM, the mosasaur would be fed six times during the day. When left to its own devices, it appears to hunt primarily during the day. When at rest, it floats in the water column rather than directly on the surface, likely rising up to breathe similarly to some modern marine animals.

Diet and Feeding Behavior

According to Jurassic World personnel, the normal diet of Mosasaurus maximus consists of fish, ammonites, birds, and marine reptiles such as turtles and smaller mosasaurs. InGen cloned great white sharks (Carcharodon carcharias) at an offsite location to be part of the mosasaur’s diet; it was fed a subadult female shark on 12/22/2015 as one of its last prepared meals, and the Jurassic World website indicates that sharks were its typical food items. Some media has portrayed it as feeding on live sharks that were apparently introduced to its habitat; these would likely have supplemented its diet during times when the feeding show was not operational. Mosasaurus tracks prey using sight and sensing vibrations including sound. Noise carries much farther underwater, making this a useful way to find live food. It has a very poor sense of smell, compounded by the fact that its tongue is not forked like other squamates.

This animal is not a picky eater, consuming virtually any available prey. Its diet includes terrestrial animals that venture too close to the water’s edge, as well as flying animals such as Pteranodon. According to the LEGO Jurassic World game, the Mosasaurus can open its lower jaw wide enough to swallow food larger than its own head, but it is not seen to do this in the films.

Jurassic World’s Mosasaurus consumes an escaped Pteranodon and Jurassic World employee Zara Young in typical predatory breaching attack, Isla Nublar (12/22/2015)

Mosasaurus tends to be a messy eater when preying on larger animals. Its first intent is to kill the victim, so it often breaks the prey apart while attacking. If it can swallow prey whole, it will attempt to; the pterygoid teeth prevent slippery prey, such as fish, from escaping and forces them toward its throat. If the mosasaur loses any chunks of prey while making the initial bite, it will usually return to consume these after swallowing the first chunk. It kills by clamping its jaws shut around the prey item, typically around the midsection or neck, slamming the prey item into the water’s surface, and thrashing it around underwater. It attacks prey from below, often breaching in the process of capturing its prey.

The mosasaur’s food is torn into chunks large enough to swallow, but it is often a wasteful eater if its prey is particularly large; for example, about half of the Indominus rex remained uneaten after it was killed by the Mosasaurus. The rear half of the animal had been consumed, leaving the skull, most of the ribcage, and one arm intact. It only eats when it is hungry, like most animals, and does not appear to store food for later, since it did not return to eat the rest of the Indominus. Animals killed in defense of its territory may be eaten even if it was not hunting at the time.

The Mosasaurus exhibits the first known case of ambush-feeding on a terrestrial prey item, Isla Nublar (12/22/2015)

Ambushing terrestrial prey is a riskier maneuver for the mosasaur, but on Isla Nublar this behavior was rewarded with much larger prey items. Few large animal remains were seen on the floor of the Lagoon, however; it is likely that this method of hunting was only used on rare occasions.

Mercenaries hired by Eli Mills and Henry Wu speculated that the Mosasaurus would have starved to death after six months without scheduled feeding, but the animal actually did survive. When deprived of its normal food sources, the Mosasaurus has been confirmed to experimentally feed on unfamiliar objects; this may lead to it attempting to consume non-food items. Such behavior led to the unfortunate deaths of the Marine One personnel in June 2016 when the mosasaur attempted to feed on an underwater vehicle.

In June 2018, the escaped Mosasaurus was seen riding large waves and observing multiple human surfers. Eyewitnesses suggest that one particular surfer was eaten after falling from his board; a second surfer was attacked via ambush shortly after. This is not typical hunting behavior for the Mosasaurus, but opportunistic feeding on a suddenly vulnerable prey item is far from unknown in predatory animals. In 2019, boaters near New Zealand filmed it ambushing a great white shark (Carcharodon carcharias) while the shark itself was in the process of capturing a New Zealand fur seal (Arctocephalus forsteri); both the fish and mammal were consumed by the mosasaur. Similarly to the case of Zara Young, the consumption of the fur seal was likely unintended, but not unwelcome.

In a deleted scene, the escaped Mosasaurus was shown tracking a pod of humpback whales (Megaptera novaeangliae). In the process of killing one, it would also have attacked and capsized a whaling ship. Stealing the catch from ships appears to have become a habit for this animal, as in early 2022 it was reported grabbing a large and well-stocked crab trap from a ship in the Bering Sea. The trap contained red king crabs (Paralithodes camtschaticus), one of the most commonly caught crab species. As it now follows a seasonal migratory route around the Pacific, its diet likely has broadened to include a range of animals; most of its diet includes mammals such as whales and large fish such as sharks. It does not hunt orcas (Orcinus orca), and instead, it has been witnessed engaging them in social hunting activities against great white sharks.

Social Behavior

Only one Mosasaurus is known to have been created, but its solitary life does not appear to cause it any distress. As a highly aggressive animal with a massive appetite, it may not need or want the company of others. Curiously, it has been seen socializing non-aggressively with orcas, even engaging in cooperative shark hunting; if other mosasaurs existed, it may be that they would work together to hunt prey.


The sheer size of the Mosasaurus inhibits its ability to move on land, and even if it were smaller, it is not adapted for terrestrial locomotion at all. As a result, it and its relatives cannot crawl onto the shore to lay eggs; instead, they are believed to have given live birth in the ocean. However, the method by which Jurassic World’s Mosasaurus was reared is unknown. InGen had previously raised a Tylosaurus in an “incubation tank,” details about which are also unknown.

Female squamates, the order of reptiles which mosasaurs belong to, have a cloaca that is used as the receptive sex organ. Male squamates have two hemipenes as sex organs. Presumably, Mosasaurus would have the same kind of sex organs as all other squamates.

Due to being the only one of its kind, the Mosasaurus from Jurassic World has not bred and is unlikely to; as a result, details about its reproductive behavior are only speculative. Fossil eggs discovered in Antarctica in 2020 have suggested the possibility that, like some modern reptiles, mosasaurs may lay vestigial leathery eggs that hatch immediately. Not all researchers agree, due to mosasaur fossils that also appear to indicate large offspring borne inside a pregnant female. These fossils indicate that animals such as Mosasaurus give live birth to small numbers of large offspring, and may even have an equivalent to the mammalian placenta. A modern lizard which uses this strategy is the shingleback. Like this lizard, Mosasaurus may offer extended parental care to its offspring, investing energy into small numbers of young in order to greatly increase their rate of survival.


As it is a solitary animal, most of the vocalizations made by the Mosasaurus are not communication. Instead, they appear to be involuntary sounds that it makes as it moves, or noises it makes to comfort itself. When it lunges at prey, it makes a bellowing noise as its jaws open, probably produced by exhalation. While handling prey, it can be heard groaning and growling. It can also be heard making wailing and moaning noises after making a kill, but also while confronting intruders in its territory; these are presumably used to threaten competitors.

Since only one has been cloned thus far, it is unknown how they would communicate with each other, but they probably would rely on visual signalling methods. Its sense of smell is poor, but its hearing and vision are strong.

Ecological Interactions

Mosasaurus maximus is an apex predator, the largest carnivorous animal on Earth at a maximum confirmed length of 84.9 feet (though long-lived healthy animals may grow much larger). As an adult, it has no predators except for others of its own kind. As with any apex predator, its actions shape its environment. It is territorial, confronting and investigating intruders in its domain by circling them at the surface. This gives it the opportunity to observe its potential rival or prey from both above and below the water.

Concept art of the Mosasaurus attacking a harpooned humpback whale and the Yūshin Maru.

When confined to the Jurassic World Lagoon, the mosasaur would have readily preyed on any other animals within its environment. It preyed on other inhabitants of Isla Nublar including Pteranodon and Indominus (causing the extinction of the latter). Smaller fish in the lagoon were later seen to be alive and well; the mosasaur preying on Pteranodons would have reduced pressure on the populations of smaller fish.

After its unintentional release from the Lagoon in June 2016, the mosasaur’s range vastly expanded. Deleted scenes demonstrate that its diet would have now included large marine mammals such as humpback whales; it also was depicted as being aggressive toward a whaling ship, which would unintentionally alleviate predatory pressure by humans on whales. On occasion, it enjoys crustaceans such as red king crabs, although it is not adapted to grab them off the seafloor. As it migrates throughout the Pacific Ocean on a seasonal basis, the animals preyed upon by Mosasaurus will vary.

Its relationship with whales is complex compared to most of its ecology. While it does hunt humpback whales, it has also been seen swimming peacefully alongside them when it is not hungry. Whether the mosasaur is curious, or simply keeping track of potential food sources for later, is unconfirmed. It does have an interesting relationship with transient orcas near New Zealand: here, it has been known to engage with them socially rather than aggressively. A pod of orcas could easily overwhelm even this huge animal, but it would likely wound or kill some before dying, so it is beneficial to both species not to fight. Instead, the reptile and mammals cooperate to locate and kill great white sharks, a prey item they both target.

Despite its huge size, Mosasaurus has not been known to host any noticeable populations of ectoparasites or commensal hitchhikers. Barnacles may settle on numerous sea creatures such as humpback whales and green sea turtles, but not all animal skins are amenable to them, and mosasaurs do not seem to be a favorable environment. Since they are quite different from most modern creatures, it may simply be that no modern sea life is adapted to live on a mosasaur’s body. Small fish are sometimes seen swimming around the mosasaur in the ocean. These may be picking dead skin, pieces of food or pests in the mouth, or just keeping close to use it for protection.

Cultural Significance

The discovery of Mosasaurus and its eventual identification as a lizard-like animal different from any present-day creature was one of the public’s first exposures to the concept of extinction. As paleontological science developed, this animal became symbolic of deep time and prehistoric extinction events; in earlier paleoart it was often depicted as a terrible sea monster, often shown in combat with other frightful creatures. This was in line with the common idea that prehistoric species were monstrous beasts that had to be eliminated in order for civilized creatures to exist. As time has gone on the depiction of Mosasaurus has changed, as we now understand it to be a natural animal like any other.

According to Universal Studios, Mosasaurus is the reptile of the Pisces astrological sign (January 20 – February 18).

In Captivity

This was the first marine reptile to be successfully exhibited in a de-extinction theme park, and the second to be cloned after Tylosaurus. Jurassic World had already built the Lagoon in central Isla Nublar by 2004, some years before the successful cloning of Mosasaurus maximus; the intent was always to exhibit marine life, but before this species could be introduced it had to be genetically engineered to survive in a modern ocean. Conditions have changed since the Cretaceous period, and human activity further alters the oceans as time goes on.

The Jurassic World Lagoon provided a sheltered environment for the Mosasaurus where its water quality, habitat safety, and food provision could always be guaranteed. It was most likely cloned in a breeding tank; it is unknown whether InGen bred its mosasaurs from surrogate squamate eggs or some type of artificial womb device. Many modern squamates are able to survive on their own as soon as they hatch or are born, so it is likely that a young Mosasaurus could be introduced to the Lagoon at a reasonably early age. Since no large predators were living there, it was a safe environment for this reptile to grow up.

Fossils already demonstrated that the Mosasaurus could reach fifty or sixty feet long, and Jurassic World’s staff discovered that this was not even its maximum size. In captivity, this animal can grow to be in excess of one hundred feet long, upending traditional ideas of vertebrate growth limits. Caring for such a huge creature is a stupendous challenge that only an exceptionally well-funded facility like Jurassic World would be capable of; it is unlikely any private citizen would be able to keep this animal, nor could the vast majority of corporations or governments. Its diet as a full-sized adult is extremely demanding and it feeds mainly on large marine life. On days when it eats six times, it can consume around 9,000 pounds of food. Its habitat needs to be extremely large as well; the Jurassic World Lagoon contained three million gallons of seawater, all filtered to ensure it was healthy, which had to be pumped in through a canal system from the ocean. Additional water could be siphoned from freshwater sources in order to adjust the Lagoon’s salinity, temperature, and water quality.

Tending to the health of this animal would also be a massive challenge. Jurassic World’s paleoveterinarians probably had to have the Asset Containment Unit secure the mosasaur for routine checkups; while similar procedures are performed with captive orcas, the mosasaur is reptilian and far larger than an orca. Additional safety measures would have to be in place to make sure it could be given proper treatment. Aquatic animals are a challenge for veterinarians because their environment naturally has higher concentrations of pathogens and parasitic organisms, which can lead to more frequent infections. The mosasaur would have had to be regularly inspected for parasites and disease, and given medical treatment to ensure it stayed healthy. Since it is too large to move onto land, paleoveterinarians would have had to treat it from boats or while diving.

Protecting visitors was another important aspect of keeping the Mosasaurus. Its habitat was surrounded by a 10,000-volt electric fence to discourage it from breaching the perimeter of the Lagoon, which was particularly important in the south where the visitor beach was located. Signage around the Lagoon discouraged visitors from trying to climb the fence or otherwise enter the Lagoon.

The Mosasaurus performs at a feeding show, approx. 3:00 PM 12/22/2015

To offset the costs of keeping this animal alive, Jurassic World capitalized on its thrilling nature as a park attraction with multiple exhibits set up to see it. The Mosasaurus Feeding Show was one of the park’s most popular shows, demonstrating the mosasaur’s feeding behavior as it was given prepared great white sharks (another huge expense, since these fish had to be bred to the point of no longer being endangered for InGen to legally use them as food). The moderate intelligence of this reptile enables it to learn simple tricks such as jumping for food. When it was not feeding time, visitors could see the animal and its environment from the safety of the Underwater Observatory, a part of the Jurassic Aquarium facility. On the surface, it could be viewed from the monorail, the Boardwalk, and rooftop viewing areas on Main Street. Despite all of these attractions, the Mosasaurus remained one of the largest expenses the park faced and probably contributed significantly to its financial difficulties in the 2010s.

Now that Jurassic World has closed and the mosasaur has been released into the wild, it is highly unlikely that it will be kept in captivity again. There are simply no organizations capable of providing for its needs.


Mosasaurus is invaluable to the history of science as one of the first genera to teach both the scientific community and the general public about deep time and extinction. When fossil skulls belonging to this animal were first discovered in the late 1700s, they were assumed to be whale bones, but later discovered to belong to a kind of reptile somewhat similar to monitor lizards or snakes. Scientists realized that it was unlike any animal living in the modern age, and this led into the discovery that many living things had existed prior to human civilization.

As one of the largest and best-studied mosasaurs, this creature has provided information about the ancient marine ecosystems that existed during the late Cretaceous period and its role as apex predator. After being brought back from extinction, it can be used for even more research (although the cloned specimen is genetically modified by necessity as part of the de-extinction process, making it different from its ancestor). Of particular interest is what it can teach scientists about marine ecology over time, such as how the oceans have changed since the Cretaceous period and how they may change in the future.


During the de-extinct animal rights debates beginning in 2017, the Mosasaurus was sometimes brought up as an example but not particularly often. This was in part due to the fact that it had escaped captivity six months after Jurassic World closed and therefore was not threatened by Mount Sibo. Despite the mosasaur’s unknown location, the Dinosaur Protection Group featured it as an adoptable animal on their website and advocated for support to find it and assess its health. At one point its status was reported as “Missing,” and its escape was stated by the DPG, but later it was merely said to be unaccounted for with status unknown. References to its escape were scrubbed from the internet by the DPG after a short time for unknown reasons.

Eventually the mosasaur was located near O’ahu, where it was filmed during a surfing competition in June 2018. It was reported to have attacked surfers by eyewitnesses and a news crew on site, prompting an evacuation of the North Shore beaches. Since then, it appears to have continued to travel the Pacific Ocean, being sighted near New Zealand in 2019. As the Mosasaurus has proven difficult to track and a hazard to ocean traffic and recreation, it is considered particularly dangerous, but so far no action has been proposed to address it. At least one possible international incident involving the escaped mosasaur has been proposed by a deleted scene for Jurassic World: Fallen Kingdom, in which the mosasaur attacked and capsized the Japanese whaling vessel Yūshin Maru after feeding on a humpback whale that the ship had harpooned. It now routinely steals catch from fishing vessels in the Bering Sea, sometimes capsizing them in the process. Who ultimately is responsible for these kinds of consequences is yet up for debate.

Mosasaurus typically hunts in nearshore environments, but frequently makes migrations that bring it outside the exclusive economic zones of any nation. As a result, it does not live within the jurisdiction of any one country for long and spends periods of time subjected only to international law; its movements are monitored by the intergovernmental Department of Prehistoric Wildlife. The United Nations Convention on the Law of the Sea, Part XII, has special provisions for the protection of the marine environment. Whether the Mosasaurus is protected or condemned under international environmental policy has yet to be determined.


While it was in captivity, the Mosasaurus was a massive tourist attraction capable of entertaining thousands of Jurassic World guests at once with its feeding behavior, simple tricks, and awe-inspiring appearance. Like all mosasaurs it regularly loses teeth and grows new ones; lost teeth from Jurassic World animals were commonly sold as souvenirs, and the teeth of this predator would have been quite impressive. Unfortunately, behind the scenes this animal had outlandishly expensive upkeep and was a major strain on the park’s finances (especially as it continued to grow, vastly exceeding the expected dimensions). This means that it was an impractical attraction at Jurassic World, and would be virtually impossible to keep in any other facility.

A more realistic way to benefit from the mosasaur would be to study it for the unique biopharmaceutical compounds it could provide. All genetically modified de-extinct animals are sources of such compounds due to their genomes containing genes that have gone extinct or are the result of genetic modification. Specifically, Mosasaurus was genetically modified to help it survive in a modern ocean, which could yield potential treatments that would help humans or other organisms survive in a changing world.

Ecologically, the Mosasaurus is an apex predator and has a drastic effect on any ecosystem it is a part of. Since it is not a natural inhabitant of the modern-day ocean, its impact is a mixed bag of unexpected benefits and predictable drawbacks; it preys on large marine life that are already threatened by overfishing and pollution, but can alleviate pressure on populations of smaller species it does not eat by consuming their predators. It feeds on Pteranodon, which has become an invasive nuisance species in coastal areas worldwide. It appears to have learned to follow whaling ships in order to feed on their victims, which has led to some violent interactions between the mosasaur and such vessels. At least one Japanese whaling ship, the Yūshin Maru, is believed to have been capsized by the Mosasaurus. This may relieve pressure on whale populations in the Pacific, since humans kill far more whales than the mosasaur does, and replacing a large whaling ship would be expensive for any government or company. It is also known to steal from other types of fishing ships, such as crab boats in the Bering Sea. Being so large means that the mosasaur is liable to severely damage most vessels it interacts with, making it an economically significant species.


As far as we are aware, there is only one Mosasaurus maximus alive today, making your odds of encountering it reasonably low. Still, it will inevitably be encountered by some number of people in the wild (and indeed, it already has), and one of those people may be you: it is better to be prepared than not. The mosasaur’s habitat is the Pacific Ocean, which it migrates around on a seasonal basis. This is because of its massive dietary needs, which cannot be sustained by one area alone. Instead, it establishes temporary territories that it defends for a period of time before moving on in search of new food sources. Sightings have been confirmed near the Hawaiian Islands, New Zealand, Alaska, and everywhere in between. If you live near the Pacific and plan on entering the ocean, keep up to date with the Department of Prehistoric Wildlife as it reports the mosasaur’s current location. Local beaches should put up warning signs if it is spotted. Even if it has not been seen directly, its presence may be given away by the disturbance or disappearance of marine megafauna, or by pieces of whale or shark carcasses clearly bitten apart by a very large animal.

Authorities in coastal regions should put up warning signs as advised by the Department of Prehistoric Wildlife if a Mosasaurus presence is likely.

This reptile hunts primarily near islands and coasts where there are plenty of large animals nearby. You are more likely to see the Mosasaurus in places where there are populations of marine mammals or large fish. Remaining fairly close to shore may help you, since the mosasaur is very large and cannot move in shallow water. It does sometimes ambush prey on shorelines, but this is only possible under certain circumstances. Coasts with steep drop-offs will allow it to attack without getting stuck too far up the shore, and strong wave action will help it wriggle its way back to deeper water. If a mosasaur has been sighted nearby, avoid these types of geographic features. The larger local waves are, the closer the mosasaur can get to shore without becoming beached. If a mosasaur is sighted and the shore is within reach, get there as quickly and calmly as you can. Try not to splash around or make large movements: unlike a shark, Mosasaurus has a poor sense of smell and is mainly a visual predator. If you can get to the beach without attracting attention to yourself, it will probably leave you alone. Once you are on shore, help others get to safety as well.

If you are in open water when you encounter this reptile, getting to safety will be more difficult, but not impossible. It is harder to avoid attention when you are floating on the surface, but remaining still might still convince the mosasaur that you are an uninteresting object it does not need to bother with. Mosasaurus will investigate unfamiliar objects by circling around them, and if you can remain very still, there is a chance it may leave you be. On the other hand, if it is hunting, this is less likely. Boats and aircraft might be able to rescue you, but an adult Mosasaurus can easily capsize most smaller boats and the animal from Jurassic World was trained to view dangling objects as food, so rescue comes with its own set of risks. The mosasaur will submerge if it is not already underwater, aim itself at you from underneath, and charge. You will probably not be able to swim out of its way unless you are exceptionally nimble in the water, and even if you manage to dodge its maw, it could still ram you with its snout or strike you with its body, stunning you and making you easy to catch. If it breaches the water, it could even land on top of you, crushing you instantly. If you are able to grab hold of its body it may be unable to eat you; try to gouge its eyes, ears, or nostrils, but remember that it can dive deeper and stay under longer than you. Do not hold onto it if it begins to dive or starts to breach out of the water to dislodge you.

The mosasaur can be distracted with bright lights, noise, and movement. Using items such as flares or noise-generating devices may divert its attention long enough for you to get to safety. If you plan on swimming in open water where mosasaurs (or other large marine predators such as sharks) are known to live, it is advisable to carry predator-deterring items with you. In the event that you find yourself under attack from a mosasaur without anything to defend yourself on hand, it may still be possible to survive. When the mosasaur makes its move, take a deep breath and curl up into a tight ball and protect your extremities. Right now your goal should be to evade the teeth: remember that there is a secondary row of teeth located in the upper palate, meant to grip prey and prevent escape. Its jaws will engulf you and it will try to swallow you. At this point, fight back. Make yourself difficult or impossible to swallow, jab the tongue or roof of the mouth with any weapons you may have, or kick and punch at the inside of the mouth. Keep yourself from the muscles of the throat, which can crush you. If it uses its tongue to try and suffocate you, claw at the tongue with your fingernails or with items such as a dive knife. Putting up enough of a fight may eventually convince the mosasaur to regurgitate you, and hopefully it will leave you alone. At this point, make for safety as quickly and quietly as you can.

You may also encounter the Mosasaurus while boating, especially if you work in the fishing industry. Fishing nets, longlines, and crab cages are all very enticing for the mosasaur since this presents it with prey that cannot escape. It has been known to leap up and grab the catch from fishing boats, just like it used to leap for its meals in Jurassic World, and this can be highly dangerous to vessels it interacts with. Always use sonar if you are fishing or boating in an area where the mosasaur has been sighted, and if a solitary massive animal appears on your sonar readout, leave the area. If you are hauling a net or cage and this is slowing you down, you may want to give up your catch. Outrunning the mosasaur is no easy task on the water. It can accelerate much faster than a large boat and can make much tighter turns. Your best bet is to cut your lines and play dead. Hopefully, the mosasaur will eat what you have caught and move on. Once it has left the area, it is safe to start your engine and vacate. You may also be at risk if you operate a whale watching or shark diving tour boat, so be aware of unusually skittish behavior in the animals and be ready to move away from the mosasaur’s prey.

This should go without saying, but do not try to use small firearms or tranquilizer darts on an adult Mosasaurus. It is too large for a single standard tranquilizer dart to sedate, and it has very thick skin. You will only do minimal damage to its exterior unless you hit a vulnerable area such as an eye. The mouth is vulnerable due to all the soft tissue, but you do not want to end up in a situation where shooting the inside of its mouth is even an option. Unless you happen to be swimming with a high-power firearm on hand, your guns will do little to a Mosasaurus. Provoking this animal is highly inadvisable. We will repeat: do not shoot this reptile. You will only make it upset.

Behind the Scenes

In real life, Mosasaurus maximus is considered to be a junior synonym to the smaller European Mosasaurus hoffmanni, meaning that they are the same species. The giant American species was named later than the European species, so the name of the European one becomes the scientifically correct name. Some paleontologists believe that differences in the skull features of the European and American specimens are significant enough that M. maximus should still be considered a separate valid species, and the Jurassic film franchise appears to agree with this classification and consider M. maximus to be separate from M. hoffmanni.

The mosasaur’s design was, at one point, going to incorporate a forked tongue like that of modern monitor lizards, which are its closest living relatives. However, Jurassic World‘s design team opted not to do so, believing that this would make the mosasaur look like too much of a fantasy animal (particularly when combined with its already-exaggerated size).

Notable Individuals

Jurassic World Mosasaurus – female individual bred for Jurassic World

Disambiguation Links

Mosasaurus sp. (L/M)

Mosasaurus (IDW-JPR)