Wednesday 13 July 2011

The Weymouth Pliosaur.

On the eighth of this month (July 2011) celebrated naturalist and broadcaster David Attenborough unveiled Dorset County Museum's newest attraction, the 2.4 m long fossilized skull of a Jurassic pliosaur from the coast of Weymouth Bay. The first parts of the skull were uncovered by a landslip in 2003, and found by amateur palaeontologist Kevin Sheehan, who collected the pieces of the skull one at a time over the next three years.

It is estimated the complete animal would have been about eighteen meters long, and the museum suspect that it may represent a new species of pliosaur, though it has not yet been formally described, and will not be until further studies are completed. The museum has made the skull the centerpiece of a display with the title 'The World's Biggest Bite'. Palaeontologist Hans Sues, of the Smithsonian National Museum of Natural History in Washington DC, in an e-mail to National Geographic Magazine, suggests that this may be premature, as pliosaurs are large animals and newer, larger specimens are not a surprise. He also questions the evidence for this claim, which has not been presented in any formal scientific literature. This seems a little churlish, as a scientific display for tourists is not a serious scientific statement, and the term 'World's Biggest Bite' does not actually mean very much - claiming the animal had the largest jaws or the hardest bite would mean more.

Weymouth Bay forms part of the Jurassic Coast, a 150 km stretch of coast running from Budleigh Salterton in Devon to Wareham in Devon, along which 185 million years of Triassic and Jurassic history are exposed. The Jurassic Coast was the first site in the UK to be granted World Heritage Site status by UNESCO. The Weymouth Pliosaur is about 155 million years old, making it Oxfordian or Kimmeridgian in age. The Oxfordian and Kimmeridgian are 'stages', subdivisions of the Jurassic 5.5 million and 4.9 million years long respectively. These were periods of extreme global warming, in which Britain was more or less completely covered by warm, tropical seas, and marine reptiles grew to extra-ordinary sizes.

The pliosaurs were a group of large plesiosaurs with elongated, powerful jaws, and short necks. The plesiosaurs were a highly successful group of Mesozoic marine reptiles, which evolved from lizard-like ancestors in the early Triassic. They had large powerful bodies, flipper-like limbs and short tails. They were not closely related to the dinosaurs (scientists are uncertain which group of reptiles the plesiosaurs are most closely related to, due to their highly derived bodies), but like them flourished throughout the Mesozoic, going extinct abruptly at the end of the Cretaceous.