- Pohlsepia mazonensis fossil reclassified from octopus to nautiloid species
- Advanced scans revealed a radula with 11 tooth-like elements, typical of nautiloids
- Decomposition before burial made the fossil appear octopus-like originally
A 300-million-year-old fossil, previously labelled as the world's oldest octopus, has been reclassified as a nautiloid, which is a shelled cephalopod related to modern Nautilus species. The fossil, Pohlsepia mazonensis, was discovered in Illinois and initially thought to be an octopus due to its eight arms and fin-like structures.
However, recent scans have revealed the actual truth. The researchers used advanced synchrotron imaging and discovered a row of tiny tooth-like structures, a radula, which is characteristic of molluscs.
The radula had 11 tooth-like elements per row, matching nautiloids, whereas octopuses typically have seven or nine.
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These findings, published on Wednesday (April 8) in the journal Proceedings of the Royal Society B, led scientists to conclude that Pohlsepia was a nautiloid, not an octopus.
"It turns out the world's most famous octopus fossil was never an octopus at all," said Dr Thomas Clements, lead author and Lecturer in Invertebrate Zoology at the University of Reading.
"It was a nautilus relative that had been decomposing for weeks before it became buried and later preserved in rock, and that decomposition is what made it look so convincingly octopus-like."
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"Scientists identified Pohlsepia as an octopus 25 years ago, but using modern techniques showed us what was beneath the surface to the rock, which finally cracked the case. We now have the oldest soft tissue evidence of a nautiloid ever found, and a much clearer picture of when octopuses actually first appeared on Earth."
"Sometimes, reexamining controversial fossils with new techniques reveals tiny clues that lead to really exciting discoveries."
This reclassification pushes back the record of nautiloid soft tissue preservation by 220 million years and suggests that octopuses evolved much later, likely during the Jurassic period.
The discovery resolves a long-standing puzzle in octopus evolution and highlights the importance of re-examining past findings with new technologies.
