Surprising reason ancient creature baffled experts for 89 years

Experts have pinpointed why other scientists made a 'dubious identification'.

A taxidermied modern coelacanth fish specimen (background) in France being carried by two men. And a sketch of an ancient example (inset).
A taxidermied modern coelacanth fish specimen (background) and a sketch of an ancient example (inset). Source: Getty

For 89 years, experts had assumed a scattered mix of fossils were once the skeleton of a long extinct crocodile-like species.

But this month researchers announced they'd identified a critical mistake other experts had made which misdirected them, resulting in scientists making an incorrect classification. They discovered many of the bones thought to be the creature’s skull actually belonged to fish which had died nearby and become fossilised.

"We reject some previous dubious identifications and show... that supposed skull elements belong to coelacanth fishes," the research, published in the journal Vertebrate Paleontology concludes.

  • Coelacanth are an ancient group of fish that are closely related to modern-day lungfish.

The fossil was dug up in 1935 in the English county of Bristol, west of London, in Triassic rocks, and was thought to be a semi-aquatic Choristodera. But to better understand the animal they compared it to a similar find from Somerset in 2018, which contained hundreds of bones from several individuals.

Evangelos Matheau-Raven in front of his 2018 fossil find.
Researchers compared the 1935 fossil with a similar one (pictured) dug up in 2018. Evangelos R. Matheau-Raven/Andrea Matheau-Raven

New scanning techniques used by the universities of Bristol and Southampton allowed its researchers to construct a 3D model of all of the bones buried in the rocks. This helped them see both fossils clearly for the first time.

And they discovered the non-fish bones in the 1935 specimen are from a large sea-lizard called a Thalattosaur.

“Some [Thalattosaurs] reached four metres in length and would have been the terrors of the seas,” Bristol University masters student Jacob Quinn said. But the species his team identified was just a tiny Pachystropheus – one of the last ever Thalattosaurs.

“[It was] 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… If it was like its relatives, it would have had lots of sharp little teeth, ideal for snatching fish and other small, wriggly prey,” Quinn added.

Rhaetian (205 million years ago) food web of the Bristol archipelago containing Pachystropheus rhaeticus. The arrows indicate who eats who - red and black means inferred, and blue arrows are based on based upon ecology and fossil associations observed during this study. Image credit: Jacob Quinn.
A food web from 250 million years ago, showing Pachystropheus rhaeticus in the Bristol archipelago. The arrows indicate who eats who. Source: Jacob Quinn.

Project supervisor Dr David Whiteside said the Pachystropheus probably lived a life similar to a modern-day otter, dining on small fish and crustaceans.

“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,” he said.

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