Overview
- The peer-reviewed study, published Wednesday in Proceedings of the Royal Society B, concludes the 300-million-year-old Pohlsepia mazonensis is not an octopus but a nautiloid.
- High-energy synchrotron scans revealed a radula—a tooth-lined tongue—with at least 11 teeth per row, a count and shape that rule out octopuses and match nautiloids.
- The radula closely aligns with Paleocadmus pohli from the same Illinois site, leading researchers to assign the fossil to that nautiloid group.
- Guinness World Records says it will rest the fossil’s 'oldest octopus' title following the new evidence.
- By removing this Paleozoic outlier, the study supports a later, Jurassic origin for crown octopuses and also marks the earliest confirmed soft-tissue nautiloid, with decay before burial at Mazon Creek likely masking its shell and features.