Using CT scans and the new specimen, the researchers identified a prehistoric marine reptile discovered in 1935 as a thalattosaur, not a choristodere. Pachystropheus reticulumpictured with a feeding Hibodon shark. Bilgeria Fish. Photo by James Ormiston
Thanks to new findings and detailed image analysis, scientists have reclassified a prehistoric marine reptile discovered in 1935 as one of the last thalattosaurs, rather than an earlier choristoderean.
Experts determined that some of the remains were in fact those of a fish, thus revealing the true identity of a local prehistoric marine reptile.
Researchers from the Universities of Bristol and Southampton Triassic The rocks, discovered in 1935, represent one of the last thalattosaurs, a large marine lizard that behaves like an otter.
For many years, this ancient animal was thought to be a type of the first choristoderean, another group of marine reptiles similar to crocodiles. Journal of Vertebrate PaleontologyThe team examined the original specimen, discovered in 1935. They called it PachistropheusThe cave, known as “Annie,” contains hundreds of bones from several humans, as well as evidence of sharks, bony fish and even land dinosaurs.
Advanced technology and features
Jacob Quinn, a MSc student in Palaeontology at the University of Bristol’s School of Geosciences, took both specimens to Southampton where they underwent a CT scan, which produced a stack of X-ray pictures that went through the block and allowed him to reconstruct a complete 3D model of everything that was buried within it.
“Thalattosaurs were around throughout the Triassic Period,” Jacob explains. “Some of them could reach lengths of up to four metres (13 feet), and they would have been terrors of the seas. But… Pachistropheus Its body was just a metre long, half of which was its long tail. It had a long neck, a tiny matchbox-sized head (which we were unable to find) and four paddles. If it was like its kin, it would have had many sharp little teeth, ideal for catching fish and other small, wiggly prey.”
![Rhaetian food chain of the Bristol Islands](https://scitechdaily.com/images/Rhaetian-Food-Web-of-the-Bristol-Archipelago-777x420.jpg)
Pachystropheus laeticus inhabits the Rhaetian (205 million years ago) food chain of the Bristol Islands. The arrows show who eats who. The red and black are guesses, the blue arrows are based on the ecology and fossil associations observed in this study. Credit: Jacob Quinn
“Until now, Pachystropheus had been identified as the first of the Choristoderes, another group of crocodile-like marine reptiles, and was held in great importance because it was the oldest,” said Professor Mike Benton, one of Jacob’s supervisors. “Jacob was able to prove that some of the bones were actually fish, and that other bones that were actually Pachystropheus indicate that it was actually a small thalattosaur. So what was thought to be the first of the Choristoderes has now been identified as the last of the thalattosaurs.”
Discovery and reconstruction efforts
Evangelos R. Massaud Raven, from Peterborough, discovered Annie whilst on holiday in Somerset in 2018 and has spent his spare time painstakingly restoring and cleaning the bones to expose them. He said: “I found a piece of fallen rock on the beach about 10 metres from the base of the cliff. I was very excited to see some fossil bones on the exposed surface. It wasn’t until a few days later that I realised the pieces, collected two days apart, fitted together perfectly. After weeks of preparation I knew something special was emerging. It took around 350 hours and almost a year to complete the specimen.”
![Evangelos R. Matteau Raven](https://scitechdaily.com/images/Evangelos-R.-Matheau-Raven-755x1200.jpg)
Evangelos R. Matteau Raven in preparation for “Annie.” Photo credit: Evangelos R. Matteau Raven/Andrea Matteau Raven
“Pachistropheus They probably lived a similar life to modern otters, feeding on small fish and other creatures. Invertebrates “The shrimp-like reptile had a long neck, a flattened tail for swimming, and surprisingly strong forelimbs for a marine animal. Pachistropheus “They may have come onto land to feed or to avoid predators. At the time, the Bristol area, and much of Europe, was a shallow sea and these animals may have lived in large groups in the warm, shallow waters surrounding the islands.”
Annie will now be housed at Bristol Museum and Art Gallery for further study.
“We’re thrilled that this incredible fossil has joined Bristol Museum and Art Gallery’s collection, thanks to the kind help from the Friends of Bristol Museum and Art Gallery. We’re excited to be able to share the story of this new fossil and all the work the team has achieved with museum visitors,” said Deborah Hutchinson, Curator of Geology at Bristol Museum and Art Gallery.
Reference: “Phylogenetic relationships and paleoecology of Pachistropheus laeticus, an enigmatic Late Triassic marine reptile (diapsid: thalattosaurinae),” Jacob G. Quinn, Evangelos R. Matteau-Raven, David I. Whiteside, John E. A. Marshall, Deborah J. Hutchinson, Michael J. Benton, 4 June 2024, Journal of Vertebrate Paleontology.
Translation: 10.1080/02724634.2024.2350408