A fossil once hailed as the world’s oldest octopus has been reclassified after new research revealed it belonged to a very different creature.
The specimen, known as Pohlsepia mazonensis, was discovered at the Mazon Creek site near Chicago and dated to around 300 million years ago.
For decades, scientists believed it represented an early octopus, pushing back the origins of the group by more than 200 million years.
However, a study published this week in Proceedings of the Royal Society B has overturned that assumption.
Researchers at the University of Reading used advanced imaging techniques to uncover hidden anatomical features, showing the fossil was in fact a decomposed nautiloid, a relative of the modern nautilus, which has tentacles and an external shell.
Lead author Dr Thomas Clements explained that the fossil’s unusual appearance was the result of weeks of decay before burial.
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“It looked octopus-like, but when we applied synchrotron imaging – beams of light brighter than the sun – we found structures that octopuses simply don’t have,” he said.
Among the key discoveries was a radula, a feeding organ lined with rows of teeth.
The fossil contained at least 11 teeth per row, compared with the seven to nine found in octopuses, further confirming its true identity.
The finding resolves a long-standing puzzle in palaeontology and highlights the role of cutting-edge technology in rewriting evolutionary history.
“Palaeontology is often seen as dusty work. But in reality, it’s an incredibly innovative science, and new tools are allowing us to uncover secrets hidden for hundreds of millions of years,” Dr Clement added.