Full Breakdown
Scientists Reclassify World's Oldest Octopus Fossil as Nautilus Relative
4/10/2026, 4:44:26 PM
Discovery and Reclassification of Pohlsepia mazonensis
Recent research has led to the reclassification of the fossil Pohlsepia mazonensis, previously recognized as the world's oldest octopus, as a relative of the nautilus. This 300-million-year-old fossil, discovered in the Mazon Creek area of Illinois, was initially identified as an octopus in 2000, suggesting that octopuses emerged much earlier than previously believed. The next oldest known octopus fossil is approximately 90 million years younger, creating a significant gap in the fossil record.
Lead researcher Thomas Clements, a zoologist at the University of Reading, noted that the fossil's interpretation has been contentious due to its ambiguous appearance. “It kind of just looks like a white mush,” he remarked, indicating the challenges in identifying the specimen. To clarify its classification, Clements and his team employed synchrotron technology, which utilizes high-energy light to examine the fossil's internal structure.
Key Findings on the Fossil's Characteristics
The analysis revealed a radula, a ribbon of teeth common to mollusks, with each row containing 11 teeth. This tooth structure is inconsistent with octopuses, which typically have seven or nine teeth per row. Clements stated, “This has too many teeth, so it can’t be an octopus,” leading to the conclusion that Pohlsepia mazonensis is instead a nautiloid.
The fossil's misidentification may have occurred because it decomposed and lost its shell before fossilization, complicating its identification. The teeth structure matched that of another nautiloid, Paleocadmus pohli, found in the same region.
Implications for Cephalopod Evolution
The reclassification of Pohlsepia mazonensis has significant implications for understanding cephalopod evolution. The initial identification had suggested an earlier emergence of octopuses, which has now been corrected, providing a more accurate timeline for the evolution of these creatures.
Guinness World Records has announced that it will no longer list Pohlsepia mazonensis as the earliest known octopus. Managing Editor Adam Millward acknowledged the research as a “fascinating discovery” and expressed anticipation for future findings.
Official Statements and Responses
Paul Mayer, manager of the Field Museum's collection of fossil invertebrates, expressed surprise at the new classification but noted that skepticism regarding the fossil's identity had existed since its original identification. He emphasized the importance of new technologies in advancing scientific understanding of fossil collections.
Clements reassured that the Field Museum should view the new evidence positively, as it now possesses “the oldest soft tissue nautilus in the world,” which adds value to its collection.
Verbatim Quotes
- “What they’re saying “It's a very difficult fossil to interpret.” — Thomas Clements, Zoologist, University of Reading
- “ — Thomas Clements, Zoologist, University of Reading “This has too many teeth, so it can't be an octopus.” — Thomas Clements, Zoologist, University of Reading
- “We will be resting the original ‘oldest octopus fossil’ title and look forward to reviewing this new evidence,” — Adam Millward, Managing Editor, Guinness World Records
The findings were published in the journal *Proceedings of the Royal Society B*, marking a significant advancement in the understanding of cephalopod evolution and fossil classification.
