Liopleurodon were massive marine animals, reaching lengths of approximately ten - thirty metres. They possessed short necks, elongated bottlenose-shaped heads with large jaws, black or grey skin, and four large flipper limbs. Liopleurodon were bullet-resistant animals, but due to the warmer conditions of their home in the Jurassic, if a Liopleurodon were to stay in colder waters for too long, it would presumably die from the cold conditions. (The Lost Island)
Some Liopleurodon lived in pods of three or so, generally not attacking one another, while others seemed to either stray off or hunt alone. Liopleurodon were carnivorous creatures which would devour both small and large animals in their underwater environment. When confronting large objects in the waters, Liopleurodon would react aggressively by ramming and biting, whether it was an inanimate object or a living animal. Liopleurodon were seen to rub their bodies along smaller objects to try and get a reaction to see if the object was living food that could be taken and devoured. (Episode 5.2)
Incursions and encountersAnomalies around Guns Island into the Atlantic Ocean in the present, where it attacked and sank a trawler boat while trying to get the cod fish on board. The Anomaly Research Centre team later encountered the Liopleurodon in the oceans, and it was resistant to bullets they fired at it, but Nick Cutter deduced that it was already dying due to the Atlantic Ocean's cold conditions so it was left to die.
A Liopleurodon came through an Anomaly into the HMS Gartside (submarine) several times; slamming into it, biting down on its tracking device and jamming its propeller. When the submarine was pulled through the Anomaly, the Liopleurodon followed it through back into its home in the Jurassic oceans.
In the Jurassic, three Liopleurodon attacked the submarine, repeatedly slamming into and scraping against it. One of them investigated a Bathyscaphe from the submarine until Matt Anderson and Abby Maitland turned the bathyscaphe's lights off to make it seem dead. Eventually, when the team ejected a Swimming Theropod from the submarine, one of the Liopleurodon devoured it, distracting the creatures long enough for the submarine to return through the Anomaly.
- In Episode 1.1, a toy of a Liopleurodon or a different type of pliosaur can be seen in Ben Trent's room.
Liopleurodon (name meaning "smooth-sided teeth") was a genus of pliosaur which lived from approximately 162 to 150 million years ago. It was estimated to have grown up to 6.39 meters (21.0 feet) long, and was the apex predators of the seas where Europe is now located.
- The image of the Liopleurodon on the cover of The Lost Island is actually a Mosasaur from Episode 1.3.
- Though never confirmed onscreen, the pliosaurs encountered in Episode 5.2 were confirmed by the creators to have been Liopleurodon.