The chance discovery of large fossil specimens in a museum drawer have led researchers to conclude there was a gigantic marine reptile called a pliosaur swimming the seas 152 million years ago, according to a recent study.
The findings from the Late Jurassic period, though fragmentary, suggest the pliosaur was about twice the size of a killer whale 鈥� and move lead study author David Martill closer to redemption. That鈥檚 due to what many researchers considered inaccurate claims he made about the size of another pliosaur in the BBC鈥檚 1999 television documentary series 鈥淲alking With Dinosaurs.鈥�
One of the episodes 鈥渟howed a 25-metre long Liopleurodon,鈥� which 鈥渟parked heated debates 鈥� as it was thought to have been wildly overestimated and more likely to have only reached an adult size of just over six metres long,鈥� according to about , published May 10 in the journal Proceedings of the Geologists鈥� Association.
Martill, who was a consultant for the episode and is currently a professor in the University of Portsmouth鈥檚 School of the Environment, Geography and Geosciences in the United Kingdom, said he got the size 鈥渉orrendously wrong.鈥�
鈥淚 based my calculations on some fragmentary material which suggested a Liopleurodon could grow to a length of 25 metres, but the evidence was scant and it caused a lot of controversy at the time,鈥� he said in a statement. 鈥淣ow we have some evidence that is much more reliable after a serendipitous discovery of four enormous (vertebrae).鈥�
鈥榁ERY FEARSOME ANIMALS鈥�
Martill recently found one of those vertebrae in a drawer of fossils at Abingdon County Hall Museum in England, and subsequently learned the curator had three more in storage. The vertebrae were large, with a maximum width of 269 millimetres (10.5 inches), maximum height of 222 millimetres (8.7 inches) and maximum length of 103 millimetres (4 inches).
Due to the size of the vertebrae and comparisons to other fossils of other species from the Mid Jurassic and Early Cretaceous periods, the researchers concluded they were closely related to pliosaurs or a similar but undescribed species, according to the study.
Topographic scans showed the reptile might have grown to between 9.8 and 14.4 metres (roughly between 32 and 47 feet) long, the authors wrote.
鈥淎lthough not yet on a par with the claims made for Liopleurodon in the iconic BBC TV series 鈥榃alking with Dinosaurs,鈥欌�� Martill added, 鈥渋t wouldn鈥檛 surprise me if one day we find some clear evidence that this monstrous species was even bigger.鈥�
Adam S. Smith, curator of natural sciences at the Nottingham Natural History Museum, Wollaton Hall, agreed.
鈥淚t isn鈥檛 out of the question that pliosaurs may have exceeded 15 metres long,鈥� Smith said via email. However, he cautioned that an increase in length corresponds with an 鈥渆xponential increase in volume 鈥� placing a biological limit on the upper size pliosaurs could reach.鈥� Smith wasn鈥檛 involved in the study.
Pliosaurs were 鈥渁 group of large carnivorous marine reptiles characterized by massive heads, short necks and streamlined tear-shaped bodies,鈥� according to Britannica. Four large fins helped propel the ancient creatures through seas. Pliosaurs were similar to plesiosaurs, their relatives in the order Plesiosauria, but had bigger elongated heads and shorter necks.
鈥淲e know these pliosaurs were very fearsome animals swimming in the seas that covered Oxfordshire 145-152 million years ago,鈥� Martill said. 鈥淭hey had a massive skull with huge protruding teeth like daggers 鈥� as big, if not bigger than, a T. rex, and certainly more powerful.
鈥淭hey 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,鈥� he added. 鈥淲e 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.鈥�
LIMITATIONS OF GUESSTIMATING SIZE
Valentin Fischer, a professor in the department of geology at the University of Liège who wasn鈥檛 part of the study, called the findings 鈥渟haky鈥� since lengths of cervical vertebrae 鈥� the type the authors analyzed 鈥� from pliosaurs can vary.
Another expert, however, thought estimates weren鈥檛 necessarily a bad thing.
鈥淪caling is always reliant on a best guess using the specimens we know,鈥� said Andrew Cuff, a UK-based paleontologist who wasn鈥檛 involved in the study, via email. 鈥淭he author in this current study seem to have done a good job comparing specimens and attempting to scale up the more complete fossil individuals so that the newly described vertebrae would fit. Whether the 14.4m is realistic or possibly too large will require more complete specimens to confirm for sure but I wouldn鈥檛 be surprised if a pliosaur that large did swim the Jurassic seas.鈥�
The vertebrae were initially found during excavations at Warren Farm in the River Thames Valley near Abingdon in Oxfordshire, and derive from the Kimmeridge Clay Formation, according to the study.
鈥淭his kind of discovery reminds us that there were some amazing animals in the past,鈥� Michael Benton, a professor of vertebrate paleontology at the University of Bristol in the UK, said via email. Benton wasn鈥檛 involved in the study. 鈥淗ere is a marine reptile as large as a sperm whale, and there鈥檚 nothing like it around today.鈥�
