Pliosaurs – Terrible Monsters of the Mesozoic Seas

A study into the potential bite force of an extinct marine reptile indicates that it was able to generate a force of around 15 Tonnes per square inch according to research information published by the Natural History Museum of Oslo.

The research summarises work done to date on newly discovered fossils of a pliosaur, an ancient marine reptile that would have terrorised the Jurassic seas and been an apex predator.

Short-necked Plesiosaurs

Pliosaurs are a short-necked variety of plesiosaur, instead of having small heads and long necks adapted to a diet of small prey items like the plesiosaurs, the pliosaurs evolved into the top predators of the Jurassic marine environment.  Pliosaurs had relatively massive skulls, armed with long, sharp teeth, that in many cases stuck out from the jaws.  These were truly fearsome predators and would have attacked and eaten any other animals in the sea.  Size estimates vary as most pliosaurs are only known from fragmentary and disarticulated remains but some of these creatures may have reached lengths in excess of 20 metres.

A Pliosaur Replica


CollectA Pliosaurus model.  A replica of a Pliosaurus marine reptile.

The picture (above) shows a scale model of a Pliosaurus, this is part of the CollectA Deluxe range of models and figures: CollectA Deluxe Prehistoric Life Models.

This new pliosaur, with the very strong bite, is a specimen found on the Norwegian archipelago of Svalbard, north of the Arctic circle.   The area is well known for marine reptile fossils, several plesiosaurs have been found and a number of pliosaurs and the Svalbard discovery may represent a new species.  Palaeontologists have been working with geological survey teams, in a bid to identify coal, oil and gas reserves, buried deep in the rocks, whilst studying the geology of the area a number of marine reptile fossils have been discovered.

To read an article about Norwegian marine reptiles: Is it a new species of Norwegian Marine Reptile or Not?

With only fragmentary fossils and partial skull material to work with; the research teams are having difficulty in establishing the taxonomy of many of their finds.  The Svalbard monster, affectionately nick-named “Predator X” by the scientists may be another specimen of a pliosaur fossil found on a different part of the island group.  Whatever it is, it would have been a formidable hunter, with an estimated length of 13 metres and a skull as long as a car.

Commenting on the bite force calculations, Joern Hurum, Associate Professor of Vertebrate Palaeontology at the Natural History Museum of Oslo stated:

“With a skull that’s more than 10 feet long you’d expect the bite to be powerful but this is off the scale.  It’s much more powerful than Tyrannosaurus rex”.


Bite force analysis on extinct animals is calculated using mathematical formulae based on the strength and composition of the skull, the morphology of the teeth and the muscle attachments for the jaws.  Comparisons are made with extant animals to give a benchmark for bite forces, as the bite exerted by animals such as sharks, dogs, and humans can all be measured; (a bite force measuring device is called a gnathodynamometer).  Humans can generate a bite force in excess of 250 lbs per square inch across their molars, large dogs have a stronger bite, as do animals such as lions that can generate up to 1,000 lbs of force per square inch.

American Alligators have a bite force in excess of this, up to 3,000 lbs, whilst work with tyrannosaur skulls indicate a bite force of 15.000 lbs for T. rex.  Still according to the international team of scientists who worked on the pliosaur fossils, it seems that this brute could generate over twice as much bite force as a Tyrannosaurus rex.

Speaking about the bite force calculations, Greg Erickson (evolutionary biologist), stated that this was probably the biggest bite force ever calculated.  This pliosaur lived during the Late Jurassic and the fossils have been dated to around 147 million years ago (Tithonian faunal stage).  Some of the fossil teeth from this animal have been estimated to be over 30 cms long, making the teeth nearly twice as big as any known meat-eating dinosaur.

The scientists have reconstructed the marine reptile from a partial skull material and 20,000 fossilised fragments of skeleton and used the fossils of other pliosaurs as a template.

A Picture of a Pliosaur (Liopleurodon Model)

Picture credit: Everything Dinosaur

The pliosaur, estimated to have weighed 45 Tonnes, was similar to but had more massive bones than another fossil sea monster found on Svalbard in 2007, also estimated at over 50 feet long and the largest pliosaur specimen discovered to date.

Bite Force Measurements

Some scientists have developed the bite force measurements in extinct and extant animals and correlated them to brain size.  After all, as well as providing anchorage for the jaw muscles the skull is essentially a protective box housing the brain.  The scientists found that the larger the bite force the smaller the brain.  This pliosaur from the Norwegian territory of Svalbard, seems to back up this particular theory.  From examinations of the brain case it is thought that this particular marine reptile had a small brain, with much of the brain volume being made up of areas dedicated to sight and the sense of smell.  Very little of the brain was dedicated to problem solving (cerebrum).

When you have a bite capable of crushing metal, perhaps you don’t need to be that smart.

To view a model of a pliosaur (Liopleurodon), other marine reptiles and dinosaurs: Dinosaur and Marine Reptile Models and Figures.