300-Million-Year-Old Fossil Reclassified as Nautilus Relative
Advanced imaging reveals that a fossil once thought to be the world's oldest octopus is actually a relative of the nautilus.
A 300-million-year-old fossil, previously identified as the world's oldest octopus, has been reclassified as a relative of the nautilus following advanced imaging analysis. The specimen, known as Pohlsepia mazonensis, was discovered in Illinois' Mazon Creek area and initially described in 2000. Its identification as an octopus suggested that these cephalopods evolved much earlier than previously believed.
Recent research led by Dr. Thomas Clements at the University of Reading utilized synchrotron imaging to examine the fossil's internal structure. The analysis revealed a radula—a ribbon of teeth—with 11 teeth per row, a characteristic feature of nautiloids. In contrast, modern octopuses possess radulae with seven or nine teeth per row. This discrepancy led researchers to conclude that Pohlsepia mazonensis is more accurately classified as a nautiloid.
Dr. Clements noted that the fossil's octopus-like appearance may have resulted from decomposition processes prior to fossilization, which obscured its original shell. He emphasized the importance of reexamining controversial fossils with modern techniques, stating that such approaches can reveal new insights into evolutionary history.
As a result of these findings, Guinness World Records has removed Pohlsepia mazonensis from its listing as the earliest known octopus. The fossil remains part of the Field Museum's collection in Chicago, now recognized as the oldest known soft tissue nautiloid specimen.