Weymouth Bay Pliosaur Skull © DCM
An enormous skull from a giant marine reptile recovered from the Dorset coast near Weymouth, has been declared as a species new to science and named in honour of its finder Kevan Sheehan. The new name, Pliosaurus kevani, is published in the on-line journal PLOS ONE this week.
Mr Sheehan said; ‘This is a great day for Kevans around the world!’
Pliosaurus was a giant oceanic predator with a skull 2 metres long and body perhaps 12 metres in length. It was in fact the most powerful, scariest marine monster of all time, capable of biting the biggest great white shark alive today, clean in half (although they never existed at the same time). Despite their giant size, the oldest Pliosaurus species had many teeth, suggesting a diet of fish but over time they developed fewer, stronger teeth suggesting they evolved to hunt large prey such as big fish and other marine reptiles; plesiosaurs and ichthyosaurs. Indeed, there are spectacular examples of bones, particularly limbs with massive bite marks; just like many of today’s predators, pliosaurs probably disabled their prey and allowed them to weaken through blood loss before going in for the kill.
Richard Edmonds and Kevan Sheehan with the Pliosaur skull © DCM
The Dorset specimen, known as the and ‘the World’s Biggest Bite’, is one of the most complete and best preserved skulls ever found and as a result it has provided new insights into our understanding of how these enormous animals evolved. Giant pliosaurs were first found in the UK in the early 1800s, but most fossils were fragmentary, so their species diversity has been uncertain. The scientific paper has taken a new look at both the Dorset specimen and two other skulls discovered near Westbury over the last 30 years (the Westbury pliosaurs are on display at Bristol City Museum and Art Gallery). That study has led to a revision of the group and the naming of both those specimens as new species as well; Pliosaurus carpenteri after the collector, Simon Carpenter and Pliosaurus westburyensis.
One of the most significant conclusions from the paper is that the genus Pliosaurus appears to have developed a highly effective body plan that remained little changed for millions of years in the Late Jurassic sea. During that time just a handful of species evolved and this is unlike most top predators in the fossil record which reach dominance but were then typically swiftly replaced by different forms. The research has been undertaken by a team of vertebrate palaeontologists from Oxford, Bristol and Cambridge universities and with Leicester, Nottingham and the Sedgwick (Cambridge) museums together with independent researchers.
Mark Evans, Curator of Natural Sciences at Leicester Museum said:
“We have so few diagnostic specimens and the extraordinary thing is that whenever a specimen is diagnostic, it often turns out to be something new. We’ve effectively doubled the number of British Pliosaurus species in the paper.”
Pliosaurus dominated the seas around 150 million years ago in the Late Jurassic and similar forms appeared again in the Cretaceous. They have been found in northern Norway on the island of Svalbard (the famous Predator X of television fame), Canada, Mexico, Colombia and Australia. Despite the huge size of pliosaurs, identifiable specimens are rare in the fossil record; there is about 1 million years between the Weymouth Bay and Westbury specimens, more than 100,000 generations, yet they are only known from three described specimens. That is because most animals do not become fossilised while, as a top predator, there are far fewer individuals than their prey source. This is the nature of the science; trying to untangle the history of life from just a handful of specimens, but that also makes it exciting as new finds, providing new insights, will always come to light so long as collectors are out there rescuing the fossils when they become exposed.
Sir David Attenborough with the Pliosaur skull – 8th July 2011 © DCM
Further studies are ongoing with Pliosaurus kevani. All the bones have been through an industrial CT scanner at the University of Southampton, Faculty of Engineering (the muVIS X-ray Imaging Centre) and the data is being analysed by students from Bristol University where they are particularly focused on the biomechanics of the skull, including the biting force of the jaws. Analysis of the scans has also resolved detailed internal structures such as blood and sensory canals and this work should be published in the near future.
The skull of Pliosaurus kevani is on permanent display at the Dorset County Museum thanks to a grant from the Heritage Lottery Fund ‘Collecting Cultures’ program with match funding from Dorset and Devon County Councils.
For further information contact the Museum on 01305 262735 or check the website on www.dorsetcountymuseum.org