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 nautilus relative, altering the evolutionary timeline of cephalopods.
A 300-million-year-old fossil, previously identified as the world's oldest octopus, has been reclassified as a relative of the nautilus.
The fossil, known as Pohlsepia mazonensis, was discovered in Illinois' Mazon Creek area and had been considered a significant find in cephalopod evolution.
Recent research led by University of Reading zoologist Thomas Clements utilized advanced 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 of nautiloids. In contrast, octopuses possess radulae with either seven or nine teeth per row.
Clements explained that the fossil's octopus-like appearance may have resulted from decomposition before fossilization, which obscured its original shell.
As a result of these findings, Guinness World Records will no longer list Pohlsepia mazonensis as the earliest known octopus.
The fossil remains part of the Field Museum's collection in Chicago.