Ancient Marine Reptile Mystery Solved Revealing Thalattosaur Instead of Early Crocodile

Photo byPhoto by Jen Palmer on Unsplash

A recent study has resolved the long-standing mystery surrounding a prehistoric marine reptile, revealing that remains initially believed to be one of the first choristoderes belonged to a thalattosaur, a giant sea lizard. Discovered in Triassic rocks in 1935, these bones were long thought to represent early crocodile-like reptiles. However, research by the University of Bristol and the University of Southampton has clarified their true identity.

The breakthrough came when researchers examined the original 1935 specimen alongside a newly discovered and well-preserved thalattosaur specimen, Pachystropheus, nicknamed 'Annie'. The study, published in the Journal of Vertebrate Paleontology, involved advanced CT scanning to create a 3D model of the fossils. This analysis revealed that while some of the bones were from fish, others belonged to Pachystropheus, which is a thalattosaur rather than a choristodere.

Pachystropheus, discovered in 2018, was painstakingly reconstructed over about a year. The specimen indicates that Pachystropheus was a small, slender thalattosaur, around one meter in length, with a long tail and neck, similar to modern otters in its aquatic lifestyle. It likely fed on small fish and invertebrates and may have come ashore occasionally.

The study provides new insights into the life of thalattosaurs and shifts the understanding of their evolutionary timeline. Pachystropheus, previously considered an early choristodere, is now identified as one of the last thalattosaurs. The specimen will be further studied and displayed at the Bristol Museum & Art Gallery.