Following new findings and detailed images, scientists have reclassified the prehistoric marine reptile discovered in 1935 as one of the last thalattosaurs rather than an early choristodera. The true identity of a local prehistoric marine reptile has been revealed after experts determined that some of its remains actually belonged to a fish.

Researchers from the Universities of Bristol and Southampton determined in 1935 that bones found in Triassic rocks came from one of the last thalattosaurs, a large sea lizard that behaved like an otter.

For many years, this ancient animal was believed to be one of the first choristoderas, another group of crocodile-like marine reptiles. However, in a published study Journal of Vertebrate Paleontology The team examined the original named sample from 1935. They compared it to a surprising new example pachystropheus Known as “Annie,” it contains hundreds of bones belonging to several individuals, as well as evidence of sharks, bony fish, and even land-dwelling dinosaurs.

Advanced methods and features

Jacob Quinn, who is studying for a master’s degree in palaeobiology at the Bristol School of Earth Sciences, took the two samples to Southampton where they were scanned with CT scans, allowing him to reconstruct a full 3D model by creating X-ray stacks between the blocks. everything buried in blocks

“Thalattosaurs were around throughout the Triassic,” Jacob explained. “Some were four meters (13 feet) long and were terrors of the seas. But our pachystropheus It was only a meter long, half of which was its long tail. It also had a long neck, a small matchbox-sized head that we couldn’t find, and four paddles. “If it were like its relatives, it would have lots of sharp little teeth that were perfect for catching fish and other small, wavy prey.”

“Pachystropheus had previously been described as the first of another group of crocodilian marine reptiles, the choristoderes, and was considered very important because it was the oldest,” said Professor Mike Benton, one of Jacob’s advisors. “Jacob was able to show that some of the bones actually came from fish, while those belonging to Pachystropheus were actually a small Thalattosaurus. Therefore, instead of being considered the first of the choristoderas, it is now described as the last of the thalattosaurs.”

Opening and reconstruction

Evangelos R. Mato-Raven of Peterborough discovered Annie while on holiday in Somerset in 2018, then meticulously dismembered and cleaned the bones to reveal them in his spare time. He said: “I noticed pieces of rock falling onto the beach about 10 meters from the bottom of the cliff. I was very pleased to see fossilized bones on its exposed surfaces. It wasn’t until a few days later that I saw that the pieces, which were put together two days apart, fit together. After a few weeks of preparation, we saw something special emerge. It took me about 350 hours and about a year to create the sample.”

” pachystropheus, It probably lived the life of a modern sea otter, feeding on small fish or invertebrates such as shrimp,” says another lead author, Dr. David Whiteside. “These slender reptiles had long necks, a flattened tail for swimming, and unusually strong forelimbs for a marine animal. pachystropheus They may come ashore to feed or avoid predators. ‘The Bristol area, like much of Europe at the time, was shallow and these animals may have lived as a large colony in the warm, shallow waters around the island archipelago.’

Annie will now remain at Bristol Museum and Art Gallery for further study.

“We are delighted that this incredible fossil is now part of the Bristol Museum and Art Gallery collection, thanks to the kind help of the Friends of Bristol Museums, Galleries and Archives. We are delighted to be able to share the story of this new fossil and all the work the team has done with museum visitors,” says Bristol Museum and Art Gallery Curator of Geology, Deborah Hutchinson.