For years, a prehistoric “weird blob” fossil sat in the imagination of both scientists and the record books—supposedly the world’s oldest octopus. It was the kind of claim that makes you pause. Not because it sounded wild, but because it actually fit so well at the time.
Misryoum newsroom reported that Thomas Clements, lead researcher behind the new work and a zoology professor at England’s University of Reading, says the fossilized remains previously listed as the earliest known octopus belong instead to a relative of a nautilus—a cephalopod with both tentacles and a shell. The specimen, called Pohlsepia mazonensis, was found in the Mazon Creek area of Illinois, about 50 miles southwest of Chicago, a place known for fossils from a period before dinosaurs walked the Earth. The creature itself was described as a blob about the size of a human hand.
What makes this so tricky is that the fossil looks… unhelpful. Clements told The Associated Press that it’s a very difficult fossil to interpret. “To look at it, it kind of just looks like a white mush.” He added that if you’re a cephalopod researcher hunting for octopuses, it can superficially resemble a deep-water octopus. Misryoum editorial desk noted that this kind of misread isn’t rare in paleontology, especially when fossils don’t preserve the features you’d most want.
The 2000 identification by paleontologists as an octopus upended thinking about cephalopod evolution, implying eight-tentacled lineages showed up much earlier than previously thought. Misryoum analysis indicates that, with the next oldest-known octopus fossil only about 90 million years old, the gap raised serious questions. “It’s a huge gap,” Clements said. “And so that big gap got researchers sort of questioning, ‘Is this thing actually an octopus?’”
To answer that, Clements and his team used a synchrotron—an instrument that uses fast-moving electrons to create light beams brighter than the sun—to peer inside the fossil rock. What they found was a ribbon of teeth known as a radula, common to all mollusks, including nautiluses and octopuses. Each row contained 11 teeth, and that detail became the deciding evidence. As Clements put it, “This has too many teeth, so it can’t be an octopus.” Octopuses have either seven or nine. The tooth pattern matched a fossil nautiloid called Paleocadmus pohli that had been found in the same area.
Clements also suggested how the confusion may have happened: the creature decomposed and lost its telltale shell before it was fossilized, complicating identification. Misryoum newsroom reported that he views the update as proof that revisiting controversial fossils with modern tools can uncover tiny clues. Sometimes, reexamining controversial fossils with new techniques reveals tiny clues that lead to really exciting discoveries—he said something to that effect in the statement. In this case, the “oldest octopus” now appears to be the oldest soft tissue nautilus in the world.
Because of the findings published this week in the journal Proceedings of the Royal Society B, Guinness World Records said it will no longer list Pohlsepia mazonensis as the earliest known octopus. Misryoum editorial team noted that Guinness Managing Editor Adam Millward described the discovery as fascinating, saying they will rest the original “oldest octopus fossil” title and review the new evidence. Pohlsepia mazonensis is named for its discoverer James Pohl, and it’s in the collection of the Field Museum in Chicago. Clements said the museum shouldn’t be disappointed, and he seemed genuinely pleased about what this means for soft-tissue nautilus research. If you’ve ever been in a museum storage room—those particular, dry paper-and-plastic smells—it’s easy to imagine the appeal of suddenly having the “wrong” label corrected.
In a way, the story is also about humility: one blob, reanalyzed, turns into a different kind of ancient animal. And then the bigger questions shift again—how early these cephalopods really emerged, and how often our first readings are limited by what the rock happened to keep.
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