More than two decades after a fossil was designated as the oldest known octopus, new findings suggest that it might not be an octopus at all.
Recent studies published in the journal Proceedings of the Royal Society B indicate that the fossil, named Paulsepia mazonensis, which dates back 300 million years and was uncovered in the Mazon Creek Fossil Beds of northeastern Illinois, is actually more akin to a nautilus than to an octopus.
This creature is believed to be a relative of the nautilus, recognized for its shell and tentacles.
Cephalopods, the category encompassing creatures like octopuses and cuttlefish, are distinguished by their tentacles, advanced nervous systems, and lack of hard skeletons.
Initially labeled as the world’s oldest octopus in 2000, this fossil is now reclassified as the oldest known soft-tissue nautilus.
Thomas Clements, a zoologist from the University of Reading and the lead investigator of this new research, noted to The Associated Press that the fossil poses significant challenges for interpretation. “It’s very difficult,” he said, adding that upon first glance, it appears as “white mush.”
He mentioned that for those studying cephalopods, the fossil superficially resembles a deep-sea octopus. However, the key differentiator was the structure of its teeth. Using advanced imaging technology, specifically a synchrotron, the researchers uncovered that each row contained 11 teeth—more than the seven or nine typically seen in octopuses.
“It can’t be an octopus because it has too many teeth,” Clements clarified.
This revelation marks a shift in understanding: the long-claimed oldest octopus is actually a fossilized nautilus. The fossil had teeth similar to those of Palaeocadomus pauli, another nautilus discovered in the same region.
Scientists believe that a mix-up occurred because the animal decomposed and lost its shell prior to fossilization.
The next oldest known octopus fossil is estimated to be around 90 million years old, which makes it roughly 210 million years younger than Paulsepia mazonensis.
“This is a significant gap,” Clements pointed out, noting that it has raised longstanding questions among researchers. “That gap led us to ask, ‘Is this truly an octopus?'”
The fossil is currently part of the collection at the Field Museum in Chicago.
Paul Mayer, who oversees the museum’s invertebrate fossil collection, expressed a bit of surprise at the reclassification but acknowledged ongoing skepticism since the fossil’s original description in 2000. “People have been questioning its identity as an octopus ever since,” Mayer commented.
He concluded that the new findings are “great for our collection,” expressing hope that future discoveries will lead to further intriguing stories.
