World’s Oldest Octopus Claim Overturned After 300 Million Year Fossil Reclassified

 A long-standing claim about the world’s earliest octopus has been overturned, after new research revealed that the 300-million-year-old fossil in question is not an octopus at all.

For years, Pohlsepia mazonensis held recognition as the oldest known octopus, even earning a place in the Guinness World Records. But a fresh scientific analysis has reclassified the enigmatic specimen as a nautiloid — a distant relative of modern-day nautilus — rather than an early octopus.

The study, led by University of Reading zoologist Thomas Clements and published in Proceedings of the Royal Society B, revisits a fossil that has puzzled scientists for decades. Discovered in the fossil-rich Mazon Creek region of Illinois, the specimen dates back to a time long before the age of dinosaurs. Roughly the size of a human hand, the fossil has often been described as little more than an indistinct, pale mass — making its classification particularly challenging.

When it was first identified as an octopus in 2000, the finding disrupted established evolutionary timelines, suggesting that octopuses existed far earlier than previously believed. The next oldest confirmed octopus fossil dates back only about 90 million years, leaving a vast and suspicious gap in the fossil record.

“That gap alone raised questions,” Clements noted, pointing out that the specimen’s ambiguous appearance had long fueled skepticism within the scientific community.

To resolve the mystery, researchers turned to advanced imaging techniques, using a synchrotron to peer inside the fossil. This method, which generates extremely intense beams of light, revealed a crucial detail: a radula — a ribbon-like structure lined with teeth, common to mollusks. However, the radula in this fossil contained 11 teeth per row, a defining feature inconsistent with octopuses, which typically have seven or nine.

That single detail proved decisive. The tooth pattern instead matched that of a known nautiloid species, Paleocadmus pohli, also discovered in the same region. Scientists believe the original misidentification likely occurred because the creature’s shell had decomposed before fossilization, leaving behind only soft tissue and obscuring its true identity.

With this new evidence, Pohlsepia mazonensis has officially lost its status as the earliest octopus. Adam Millward of Guinness World Records described the revision as “a fascinating discovery,” confirming that the title will be withdrawn pending review of the updated findings.

The fossil, originally discovered by James Pohl and now housed at the Field Museum in Chicago, remains scientifically significant despite the reclassification. According to Paul Mayer, questions about its identity have persisted since its initial description more than two decades ago, and the new findings reflect the growing impact of modern technology on paleontological research.

Rather than diminishing its importance, the revised classification may enhance it. As Clements points out, the fossil is now considered the oldest known example of a soft-bodied nautilus — a rare and valuable addition to the scientific record.

In the end, what was once thought to rewrite the history of octopuses has instead provided a deeper understanding of ancient marine life, underscoring how evolving technologies continue to reshape even the most established scientific narratives.