An Ultimate Guide to the Pliosaurus: Predator X

Leave a comment / / Updated on: 19th December 2023

Name MeaningMore LizardHeightN/A
PronunciationPLY-oh-SORE-usLength8–12 meters (26.2–39.4 feet)
EraMesozoicLate JurassicWeight5–11 metric tons (5.5–12.2 short tons)
ClassificationSauropterygia,‭ Plesiosauria & PliosauridaeLocationEurope, South America, and possibly Asia

Pliosaurus Pictures

Pliosaurus Funkei swimming | Racksuz via Getty Images

The Pliosaurus

Gage Beasley Prehistoric's Pliosaurus Concept
Gage Beasley Prehistoric’s Pliosaurus Concept

If you’ve ever heard of the giant, ferocious Predator X discovered in Norway, you’re already acquainted with Pliosaurus – the prehistoric marine reptile living in our planet’s Late Jurassic seas.

Having lived between 155 and 147 million years ago, the Pliosaurus is now among the most famous prehistoric creatures thanks to its large size, massive skull, and enormous teeth. 

Its strong bite force did nothing but bring it to more people’s attention!

However, the fossils discovered in Norway weren’t the first ones attributed to the genus. 

The story actually goes back to the 19th century. Read on to discover more!

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Physical Characteristics

Pliosaurus | Racksuz via Getty Images

The Pliosaurus was a massive marine pliosaurid reptile. 

It had a robust skull, a short yet sturdy neck supporting the enormous skull, and a muscular, teardrop-shaped body.

Its skull was unusually large, measuring approximately 3 meters (9.8 feet) long. Can you imagine this? 

The teeth only measured 30 centimeters (11.8 inches) long and had massive roots that made them steady and strong. 

Pliosaurus teeth are considered a distinguishing characteristic of the genus primarily because they are triangular in cross-section.

Some sources list that the Pliosaurus had 30–38 teeth on each mandibular ramus and 10-12 pairs of teeth adjacent to the mandibular symphysis. 

Teeth of P. kevani | Photo via A Giant Pliosaurid Skull from the Late Jurassic of England (Benson et al., 2013) (CC BY 2.5)

However, these numbers may vary between species.

Predator X also had two sets of wing-shaped paddles that helped it swim fast. 

The fore-flippers were likely used to travel leisurely, while the back flippers helped gain extra speed during hunting. 

The forelimbs were relatively longer compared to the forelimbs of other pliosaurids. 

The maximum size of the Pliosaurus is believed to be 8–10 meters (26.2–32.8 feet) long, with a weight of 5–11 metric tons (5.5–12.2 short tons). 

Gage Beasley Prehistoric’s Pliosaurus Size Comparison Chart

Other sources, however, argue that Predator X could grow up to 12–15 meters (39.4–49.2 feet) long!

But the most fascinating aspect in terms of size is how large the skull was. 

Can you imagine that the skull of a Pliosaurus carpenteri specimen measured 1.8 meters (5.9 feet) long?! 

That’s the height of a human being!

The skull of Pliosaurus funkei was even longer, measuring 1.6–2 meters (5.2-6.6 feet). 

Pliosaurus Funkei | Racksuz via Getty Images

Another specimen of the same species had a 2.5-meter-long (8.2 feet) skull! Additionally, the length of its forelimb was estimated at 3 meters (9.8 feet). 

Based on these numbers, scientists estimate a total body length of 10–12 meters (32.8–39.4 feet) for the species.

If you think that’s a large skull, wait until you hear about a Pliosaurus rossicus specimen! 

The skull of one specimen was estimated to have had a length of more than 3 meters (9.8 feet)! 

The size of this species was estimated at 10 meters (32.8 feet) long, while the weight was 11 metric tons (12.1 short tons).

Skull of Pliosaurus rossicus Novozhilov, 1948 | Carpenter, Kenneth via Wikipedia (CC BY-SA 4.0)

Other species, like Pliosaurus carpentri, are thought to have been smaller, reaching only 8 meters (26.2 feet) long and weighing 5 metric tons (5.5 short tons).

Considering the large skull size, it’s no wonder the Pliosaurus brain was also remarkably large. 

Supposedly, it resembled the Y-shaped brain known in great white sharks and had roughly the same size – approximately 60 centimeters (23.6 inches) long.

The eyes were remarkably large and located at the side of the head, providing the Predator X with a wide field of vision. 

Scientists discovered no ear bones, suggesting that the Pliosaurus had no sense of hearing.

Habitat and Distribution

Pliosaurus lived in today’s Europe, South America, and possibly Asia. Its fossils were unearthed in the following locations:

  • Kimmeridge Clay Formation, England
  • Svalbard archipelago, south of Sassenfjorden, Agardhfjellet Formation, Norway
  • Volga River, Russia
  • Vaca Muerta Formation, Neuquén Province, Argentina
  • Possibly Kazakhstan

Pliosaurus may have had an even wider distribution, which only new fossil discoveries can confirm!

The marine environment probably varied slightly depending on this reptile’s exact location and timeline. 

Grey cliffs of Upper Kimmeridge Clay above the beach at Egmont Bight | Jim Champion via Wikipedia (CC BY-SA 2.0)

For example, the ecosystem of today’s Agardhfjellet Formation was a shallow marine environment during the Late Jurassic. 

It had a depth of approximately 150 meters (490 feet).

Although this particular environment registered low oxygen levels, scientists believe this is not valid for all marine ecosystems. 

Instead, it may have been just a seasonal phenomenon.

Behavior and Diet

Cast skeleton and skull of Pliosaurus rossicus, Wyoming Dinosaur Center | Carpenter, Kenneth via Wikipedia (CC BY-SA 4.0)

The Pliosaurus may rank at the top of the world’s fiercest known marine predators! 

Its enormous size, massive skull, powerful jaws, and numerous large teeth allowed it to catch anything it set its eyes on!

Studies estimate that its bite force was approximately 9,617-16,927 N at the anterior dentary tooth and as much as 27,685-48,728 N at the 36th dentary tooth pair. 

If you’re just as confused as we are by these numbers, keep reading, as we’ve made some comparisons.

A human being has a bite force of only 749 N. A lion has a bite force of 4,169 N. 

A saltwater Crocodile has a bite force of 16,414 N, while a great white shark (often compared to Predator X) has a bite force of 18,216 N. 

T-Rex bite | feellife via Getty Images

A T-Rex has a maximum bite force of 57,158 N.

As such, a Pliosaurus bite can cause as many as 2-3 simultaneous great white shark bites. 

A Pliosaurus bite is almost as strong as that of a T-Rex! 

Some sources even list that the force of a Pliosaurus bite equals the force a human being would feel if crushed by an elephant!

Considering that its skull was larger than a T-Rex skull, this shouldn’t surprise us!

As stated, the Pliosaurus could probably kill whatever it went after. 

Predator X aka Pliosaurus funkei | Racksuz via Getty Images

Scientists believe it fed on various fish species, cephalopods, and even other marine reptiles

A pliosaur discovered in Australia revealed fossils of a turtle rib inside it, indicating that pliosaurids were strong enough to crush turtle shells and feed on them.

Since scientists assume that Predator X relied on its back flippers to gain extra speed, it probably pursued its prey rather than ambushed it. 

Its good eyesight helped during hunting, since it provided a wide field of vision. 

Although the Pliosaurus probably couldn’t hear anything, it could feel vibrations. 

It is believed that Predator X also possessed an excellent sense of smell.

Life Cycle

P. rossicus restoration | Bogdanov dmitrchel via Wikipedia (CC BY 2.5)

Although reptiles are typically oviparous (reproduced by laying eggs), some ancient marine reptiles adapted to a viviparous reproductive mode. 

This means that the embryo developed within the mother, who gave birth.

While this hasn’t been fully confirmed for plesiosaurs, at least some ichthyosaurs (marine reptiles) are known to have borne live young. 

This prompted scientists to suspect that ichthyosaurs weren’t the only marine reptiles with viviparous reproductive behavior.

Life restoration of an individual giving birth | Nobu Tamura via Spinops (CC BY-SA 3.0)

That is, until 1987, when a paleontological discovery revealed a 5-meter-long (16.4 feet) pregnant Polycotylus latippinus plesiosaur. 

This finding confirmed that plesiosaurs gave birth to large juveniles measuring approximately 1.5 meters (5 feet) long. 

The adults may have offered a certain degree of parental care.

Apart from this, little is known about the reproductive behavior and life cycle of the Plesiosaurus, as its ontogeny is poorly studied because of a lack of fossils.

Evolution and History

Predator X, the Pliosaurus | Racksuz via Getty Images

Plesiosaurs evolved from prehistoric aquatic reptiles that form the Sauropterygia group. 

More precisely, their ancestors likely belonged to the Eusauropterygia subgroup.

During the Upper Triassic, this subgroup split into Nothosauroidea and Pistosauria, plesiosaurs being part of the latter. 

While their ancestors used their tails to swim, pistosaurians relied on their flippers, and their vertebral columns became stiffer. 

Additionally, they were warm-blooded and gave birth to live young. 

Not all pistosaurians had a fully aquatic lifestyle. 

Pliosaurus brachydeirus flipper (cast), Wrexham Museum, Wales. | Rept0n1x via Wikipedia (CC BY-SA 3.0)

Some of the earliest members of the group were primarily coastal animals.

Years passed, and during the Late Triassic, an advanced pistosaurian group appeared – Plesiosauria

The members of this group featured flat pelves, pointed flippers, reinforced shoulder girdles, stiff limb joints, more hand and foot phalanges, and a shortened tail.

The earliest plesiosaurs were much smaller than Pliosaurus, measuring only 5 meters (16.4 feet) long. 

Only approximately 180 million years ago did they evolve to grow larger. 

By the middle Jurassic, they had body lengths of 17 meters (55.8 feet) and skulls of 3 meters (9.8 feet) long.

Pliosaurus brachydeirus | Dmitry Bogdanov via Wikipedia (CC BY-SA 3.0)

The type species of the Pliosaurus genus is Pliosaurus brachydeirus

It was named in 1841 by Richard Owen. At the time, it was called Plesiosaurus brachydeirus and was considered a wastebasket taxon in its own Plesiosaurus (Pleiosaurus) subgenus – this means that these fossils did not fit anywhere else on the taxonomic tree.

In 1842, Owen published another paper in which he created a separate genus for the species and misspelled it Pliosaurus. The name stands until today.

The following years revealed a myriad of Pliosaurus specimens that were classified into multiple species that aren’t fully recognized today.

By far the most renowned species is Pliosaurus funkei. It is also the species that gave birth to the nickname Predator X

Restoration of P. funkei | ДиБгд via Wikipedia (CC BY-SA 4.0)

The two partial skeletons associated with the species were recovered from Norway’s Svalbard archipelago. 

They were found within 2 kilometers (1.2 miles) of each other, alongside other marine reptile fossils.

The discovery occurred relatively recently. The species was named and described in 2012. 

Considering that the news crossed the world much more quickly than in the 19th century, these fossils aroused the interest of thousands of wildlife enthusiasts! 

Some pieces of news claimed that Pliosaurus funkei was the most fearsome aquatic animal ever!

Interactions with Other Species

Evolution in the past, by Henry R. Knipe, with illustrations by Alice B. Woodward and Ernest Bucknall. | Knipe, Henry Robert via Biodiversity Library

Since the Pliosaurus preyed on fish and cephalopods, we can safely assume that they were abundant in the ecosystem and included Leptolepis, Craspedites, and Kachpurites

Can you imagine how many fish the giant Pliosaurus required a day?! Definitely a lot!

Europe and South America are renowned for hosting multiple marine turtles during the Late Jurassic, which may have even fallen prey to the Pliosaurus.

Ophthalmosauridae ichthyosaurs were quite common as well during the Late Jurassic. 

They were found worldwide, so we cannot exclude the possibility that the Pliosaurus crossed paths with some. 

Pliosaurus Funkei swimming | Racksuz via Getty Images

The Keilhauia, for example, has been discovered in Norway’s Adarghfjellet Formation alongside other ichthyosaurs. 

It was a dolphin-like marine reptile measuring approximately 4 meters (13.1 feet) long.

Pliosaurus funkei specimens were unearthed alongside other marine reptiles, indicating they shared the same habitat. Here are some of them:

  • Colymbosaurus svalbardensis – a 5-meter-long (16.4 feet) cryptoclidid plesiosaur
  • Spitrasaurus – a cryptoclidid plesiosaur
  • Djupedalia – a cryptoclidid plesiosaur
  • Cryopterygius – an ophthalmosaurid ichthyosaur measuring 3.5–4 meters (11.5–13.1 feet) long
  • Palvennia – an ophthalmosaurid ichthyosaur measuring 3–4 meters (9.8–13.1 feet) long.

Cultural Significance

P. kevani holotype skull | Photo via A Giant Pliosaurid Skull from the Late Jurassic of England (Benson et al., 2013) (CC BY 2.5)

Although the genus was coined in the 19th century, it started gaining popularity only in the 21st century upon the discovery of Pliosaurus funkei

At the time, it was one of the most fascinating paleontological revelations, which aroused the interest of scientists and enthusiasts from around the world.

That’s how the nickname Predator X appeared. In reality, the translation of the genus name has nothing to do with Predator X

The term Pliosaurus comes from the Ancient Greek words pleion, which means more, and sauros, which means lizard.

Pliosaurus in Planet Dinosaur | Photo via Planet Dinosaur Wiki

However, since the media named Pliosaurus funkei our world’s most fearsome marine creature, it was nicknamed Predator X and remains renowned under this nickname as the most famous plesiosaur!

The discovery of this species was followed by a television program called Predator X

It is a documentary following the excavation of a giant marine creature that would become Pliosaurus funkei.

Predator X is also a character in Planet Dinosaur, Jurassic World: The Game, Jurassic Park Builder, and Dinosaur Train.


Pliosaurus was a large marine reptile inhabiting the Late Jurassic seas of Europe, South America, and possibly Asia.

The genus is most renowned for its massive skull, which was larger than a human being! 

Only its teeth measured 30 centimeters (inches). Just imagine how powerful this pliosaurid’s bite was!

Without a doubt, Pliosaurus could kill anything it set its eyes on, typically a fish, a cephalopod, or another marine reptile.

Commonly known as Predator X, Pliosaurus is now a favorite for wildlife enthusiasts who continue to marvel at its uniqueness, ferocity, and power! 


Is Pliosaurus bigger than Kronosaurus?

Pliosaurus and Kronosaurus probably had similar size, measuring 10 meters (32.8 feet) on average. 

However, some estimations indicate that Pliosaurus could have exceeded this length.

What is the difference between a plesiosaur and a pliosaur?

The term pliosaur refers only to the members of the Pliosaurus genus, while the term plesiosaur refers to the members of the Plesiosauria order. 

As such, all pliosaurs were plesiosaurs, but not all plesiosaurs were pliosaurs.


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