300-Million-Year-Old "Octopus" Was Never an Octopus

Scientists just corrected a case of mistaken identity that's been fooling the world for 25 years.

A 300-million-year-old fossil from Illinois called Pohlsepia mazonensis held the Guinness World Record for the earliest known octopus. But new research published in April reveals it was never an octopus at all.

The fossil fooled paleontologists for decades because the creature had been decomposing for weeks before it fossilized. That decay made it look remarkably octopus-like, complete with what appeared to be eight arms and fins.

Thomas Clements, a paleontologist at the University of Reading in England, decided to take a fresh look at the mysterious specimen. His team used synchrotron imaging, a powerful X-ray technique that uses superbright light beams to see beneath the fossil's surface.

What they found solved the puzzle. The creature had a radula, a tongue-like body part covered in rows of teeth that only mollusks possess. Octopuses do have radulas, but theirs feature either seven or nine teeth per row.

This fossil's radula had at least 11 teeth per row. That number, plus the distinctive shape of those teeth, pointed to a completely different identity: a relative of the modern nautilus, which has 13 teeth per row.

Why This Inspires

This discovery shows how new technology helps us understand our planet's history more accurately. The synchrotron imaging revealed details that earlier scientists simply couldn't see with the tools available to them.

Even better, the correction didn't erase a record. It created a new one. Pohlsepia is now the oldest soft tissue evidence of a nautiloid ever found, giving scientists a clearer picture of when these shelled cephalopods first appeared.

The finding also clarifies when octopuses actually entered Earth's story. With Pohlsepia out of the picture, evidence now points to octopuses emerging during the Jurassic period, between 145 million and 201 million years ago, rather than 300 million years ago.

Guinness World Records has already responded, with senior managing editor Adam Millward congratulating the University of Reading on their research and retiring the original title.

Alexander Pohle, a paleontologist who wasn't involved in the study, celebrated the news. He noted that serious doubts about Pohlsepia's octopus identity had existed for some time, and called the detailed work "great to see."

Sometimes correcting our mistakes leads to even better discoveries than we started with.