Chance discovery in museum leads to a breakthrough in understanding a massive marine reptile

University of Portsmouth researchers discovered evidence of a 14.4-meter-long pliosaur, challenging previous estimates of the creature's size.
Kavita Verma
University of Portsmouth paleontologists challenge previous estimates of pliosaur size
University of Portsmouth paleontologists challenge previous estimates of pliosaur size


A new species of marine reptile, that may have reached a whopping 14.4 meters in length, has been discovered by University of Portsmouth paleontologists.

Megan Jacobs, a co-author of the paper, accidentally discovered four huge vertebrates while photographing an ichthyosaur skeleton at the Abingdon County Hall Museum in Oxfordshire.

Pliosaurs were massive fearsome predators

In the Late Jurassic oceans 145–152 million years ago, pliosaurs were the leading predators. They had four flippers that served as strong paddles to propel them through the water, as well as massive skulls with teeth as big as a T. rex and enormous protruding teeth. They may have eaten smaller marine crocodiles, long-necked plesiosaurs, and ichthyosaurs by biting them and ripping portions off of them, according to Professor David Martill, lead author of the paper.

Bite marks on ichthyosaur bones, in specimens on exhibit at The Etches Collection in Dorset, demonstrate that the pliosaurs wiped out lesser marine reptiles.

The vertebrae that Professor Martill discovered are closely connected to a species of Pliosaurus. The vertebrae originate from the Kimmeridge Clay Formation, which dates back to the Late Jurassic period and is thought to be roughly 152 million years old, and were initially found during apex excavations at Warren Farm in the River Thames Valley in Oxfordshire. 

The paleontologists estimated that this specific pliosaur species may have grown to a length between 9.8 and 14.4 meters after performing topographic scans.

Correcting previous size estimates

Previous size estimations that were believed to be overestimated have been rectified as a result of the finding of this new pliosaur species. The BBC's 'Walking with Dinosaurs' television documentary series included a 25-meter-long Liopleurodon, which sparked contentious discussions about the size of this pliosaur. 

As a consultant on the BBC's Cruel Sea pilot, Professor Martill used fragmented data in his calculations, which at the time generated a lot of debate. The four huge creatures that were accidentally found in the Oxfordshire museum, however, have offered far more trustworthy proof.

New evidence may lead to more discoveries

Professor Martill thinks there may be additional evidence to support the idea that this enormous species was much bigger, albeit it is still not at par with the claims made for Liopleurodon in the venerable BBC television series - Walking With Dinosaurs. 

It's amazing to show there was an actual, truly enormous pliosaur species in the Late Jurassic oceans, he added. "If one day we discover concrete proof that this huge species was even larger, it wouldn't surprise me".

The identification of this new species and the size estimates derived from the discovered vertebrae may pave the way for future discoveries of more species of enormous sea reptiles.

Study Abstract: 

Four isolated cervical vertebrae from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Abingdon, Oxfordshire, England are identified as from a pliosaurid plesiosaurian sauropterygian on account of their shortness relative to width and height, their near platycoelous nature and the location of tall rib facets on the centrum body. They are noteworthy for their size, with a maximum width of 269 mm, maximum height of 222 mm and maximum length of 103 mm. Simple scaling and comparisons with cervical vertebrae of Mid Jurassic pliosaurs Peloneustes and Liopleurodon, and the Early Cretaceous Stenorhynchosaurus and Sachiasaurus suggest a total body length of between ~ 9.8 m and 14.4 m for the Abingdon Kimmeridge Clay pliosaur. Likely the true length was towards the higher end of this range.

A genus and species cannot be confidently determined on the basis of the described material, but they likely belong to Pliosaurus sp. or a similar animal, for which a precise neck length is not known. We estimate a neck length of 0.77 m for Pliosaurus ?brachyspondylus based on the average cervical lengths provided for specimen CAMSM J.35991.

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