300-Million-Year-Old Fossil Reclassified as Nautilus Relative, Not Oldest Octopus
New research reveals that the fossil Pohlsepia mazonensis, once considered the world's oldest octopus, is actually a relative of the nautilus.
A 300-million-year-old fossil, Pohlsepia mazonensis, previously identified as the world's oldest octopus, has been reclassified as a relative of the nautilus. This conclusion follows advanced imaging techniques that revealed anatomical features inconsistent with octopuses.
Discovered in Illinois in 2000, Pohlsepia mazonensis was initially thought to be an octopus, suggesting that these cephalopods evolved 150 million years earlier than previously believed. However, recent studies using synchrotron imaging—a method employing intense light beams to examine fossils in detail—uncovered a radula with 11 teeth per row, a characteristic of nautiloids. In contrast, octopuses typically have seven or nine teeth per row.
Dr. Thomas Clements, lead researcher and Lecturer in Invertebrate Zoology at the University of Reading, stated, :
"It turns out the world's most famous octopus fossil was never an octopus at all. It was a nautilus relative that had been decomposing for weeks before it became buried and later preserved in rock, and that decomposition is what made it look so convincingly octopus-like."
The findings, published in the journal Proceedings of the Royal Society B, indicate that the fossil's soft tissue preservation represents the oldest known example for a nautiloid. This reclassification suggests that octopuses likely evolved during the Jurassic period, aligning with previous evolutionary timelines.
As a result of this discovery, Guinness World Records will no longer list Pohlsepia mazonensis as the earliest known octopus. Managing Editor Adam Millward commented, :
"We will be resting the original 'oldest octopus fossil' title and look forward to reviewing this new evidence."
Pohlsepia mazonensis, named after its discoverer James Pohl, is housed at the Field Museum in Chicago. Dr. Clements noted that the museum now possesses "the oldest soft tissue nautilus in ... ," highlighting the significance of the specimen in understanding cephalopod evolution.