Paleontologists have unearthed four cervical vertebrae of Jurassic pliosaurid in the Kimmeridge Clay Formation near Abingdon, Oxfordshire, England.
The specimens are noteworthy for their size, with a maximum width of 27 cm, maximum height of 22 cm and maximum length of 10 cm.
Simple scaling and comparisons with cervical vertebrae of other Jurassic and Cretaceous pliosaurs suggest a total body length of between 9.8 m and 14.4 m for the Kimmeridge Clay pliosaur; likely the true length was towards the higher end of this range.
Pliosaurs were a type of short-necked plesiosaur: marine reptiles built for speed compared to their long-necked cousins.
They lived between 220 million years ago (Triassic period) and 70 million years ago (Cretaceous period) and were mostly found in the prehistoric seas that covered modern-day Europe.
Also known as pliosauroids, pliosaurs were not dinosaurs, but distant cousins of modern turtles.
They had four powerful flipper-like limbs, large crocodile-like heads, extremely powerful jaws and enormous teeth, and hunted fish, cephalopod mollusks and other marine reptiles.
“Despite their spectacular size, pliosaurids were relatively unknown in the public domain, until airing of the BBC TV animated documentary series Walking with Dinosaurs in 1999 when, in the episode, Cruel Sea a ‘star’ animal, the Middle Jurassic pliosaur Liopleurodon was controversially claimed to have been 25 m in length and to have weighed perhaps 150 tons,” said University of Portsmouth’s Professor David Martill and his colleagues.
“There is no unambiguous fossil evidence for any of these claims, with near complete Liopleurodon ferox skeletons indicating a length closer to 6.4 m.”
“There are, however, a number of isolated pliosaur bones from the Oxford Clay and Kimmeridge Clay formations of southern and eastern England that are from considerably larger individuals, though their generic identity remains largely unknown, as do their total dimensions.”
In their research, the paleontologists examined four associated pliosaur cervical vertebral centra from the Kimmeridge Clay Formation of south-central England. This deposit is Late Jurassic in age, around 152 million years old.
They calculated this marine reptile could have grown to between 9.8 and 14.4 m long.
“We know these pliosaurs were very fearsome animals swimming in the seas that covered Oxfordshire 145-152 million years ago,” Professor Martill said.
“They had a massive skull with huge protruding teeth like daggers — as big, if not bigger than a T. rex, and certainly more powerful.”
“They were at the top of the marine food chain and probably preyed on ichthyosaurs, long-necked plesiosaurs and maybe even smaller marine crocodiles, simply by biting them in half and taking chunks off them.”
“We know they were massacring smaller marine reptiles because you can see bite marks in ichthyosaur bones in examples on display in The Etches Collection in Dorset.”
“It’s wonderful to prove there was indeed a truly gigantic pliosaur species in the Late Jurassic seas,” he said.
“Although not yet on a par with the claims made for Liopleurodon in Walking With Dinosaurs, it wouldn’t surprise me if one day we find some clear evidence that this monstrous species was even bigger.”