Monster of the Sea: Peterborough scientist solves mystery of prehistoric 'terror of the sea' that hunted when dinosaurs ruled the earth

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Annie the Pachystropheus was found by Evangelos R. Matheau-Raven from Peterborough while on holiday in Somerset – and those remains have held the key to solving a decades old mystery about another prehistoric sea monster

Peterborough scientists have helped solve a mystery surrounding a 200 million year old giant sea monster that hunted while dinosaurs ruled the earth

A Pachystropheus skeleton, named Annie, found by Evangelos R. Matheau-Raven from Peterborough while on holiday in Somerset six years ago has revealed answers surrounding a similar creature found nearly 100 years ago.

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Pachystropheus were a type of thalattosaur, a large sea-lizard that behaved like an otter during the Triassic period, when the first dinosaurs were roaming the planet.

Reconstruction of Pachystropheus rhaeticus, figured alongside a hybodont shark feeding on a Birgeria fish. Image: James OrmistonReconstruction of Pachystropheus rhaeticus, figured alongside a hybodont shark feeding on a Birgeria fish. Image: James Ormiston
Reconstruction of Pachystropheus rhaeticus, figured alongside a hybodont shark feeding on a Birgeria fish. Image: James Ormiston

Now the fossils of the remarkable beast found in 2018 have been compared to a the remains of a similar creature, that was found in 1935.

For years it was assumed the ancient animal found in 1935 was one of the first choristoderes, another group of crocodile-like marine reptiles.

But now it has been examined again, it is thought it it is also a Pachystropheus.

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‘Lots of sharp teeth’

Preparation of ‘Annie’. Image: Evangelos R. Matheau-Raven/Andrea Matheau-RavenPreparation of ‘Annie’. Image: Evangelos R. Matheau-Raven/Andrea Matheau-Raven
Preparation of ‘Annie’. Image: Evangelos R. Matheau-Raven/Andrea Matheau-Raven

Jacob Quinn, from Peterborough, who is studying for his Masters in Palaeobiology at Bristol’s School of Earth Sciences, travelled with the two specimens to Southampton where they were CT scanned, producing stacks of X-rays through the blocks that allowed him to reconstruct a complete 3D model of everything buried in the blocks.

“Thalattosaurs existed throughout the Triassic,” explained Jacob. “Some of them reached four metres (13 feet) in length and would have been the terrors of the seas. But our Pachystropheus was only a metre long, and half of that was its long tail. It had a long neck too, a small head the size of a matchbox, which we haven’t found, and four paddles. If it was like its relatives, it would have had lots of sharp little teeth, ideal for snatching fish and other small, wriggly prey.”

“Previously Pachystropheus had been identified as the first of the choristoderes, another group of crocodile-like marine reptiles, and it was treated as very important because it was the oldest,” said Professor Mike Benton, one of Jacob’s supervisors. “Jacob was able to show that some of the bones actually came from fishes, and the others that really belonged to Pachystropheus show it was actually a small thalattosaur. So, from being regarded as the first of the choristoderes, it’s now identified as the last of the thalattosaurs.”

‘Something special’

Evangelos R. Matheau-Raven of Peterborough discovered Annie while on holiday in Somerset in 2018, and he then painstakingly pieced it back together and cleaned it to expose the bones in his spare time. Inside Annie there were hundreds of bones from several individuals, as well as evidence of sharks, bony fish, and even terrestrial dinosaurs.

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Evangelos said: “I spotted parts of a fallen rock on the beach about 10m from the base of the cliff. I was thrilled as their exposed surfaces showed some fossil bones.

“It wasn’t until a few days later that I could see that the pieces collected two days apart fitted together. After a few weeks of preparation, we could see that something special was emerging.

“The specimen took me some 350 hours and about a year to complete.”

Dr David Whiteside, another supervisor at Bristol, said: ““Pachystropheus probably lived the life of a modern-day otter, eating small fish or invertebrates such as shrimps

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“These slender reptiles had long necks, a tail flattened for swimming, and remarkably robust forelimbs for a marine animal, which suggests Pachystropheus may have come onto land to feed or to avoid predators. At the time, the Bristol area, and indeed much of Europe, was shallow seas, and these animals may have lived in a large colony in the warm, shallow waters surrounding the island archipelago.”

Cathedral exhibition

Annie will now be housed Bristol Museum & Art Gallery for further study.

Bristol Museum & Art Gallery geology curator, Deborah Hutchinson said: “We are very happy that this incredible fossil is now part of the collection at Bristol Museum & Art Gallery, thanks to the kind assistance from the Friends of Bristol Museums, Galleries & Archives.

“We are excited to be able to share the story of this new fossil and all the work the team have has achieved with visitors to the museum.”

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Peterborough Cathedral will be holding a ‘Monsters of the Sea' exhibition from July 15. While the two Pachystropheus will not be part of the exhibition, visitors will be able to learn more about other prehistoric marine reptiles – as well as more modern ‘terrors of the sea.’

For more information, visit https://www.peterborough-cathedral.org.uk/