Reclassification of 300-Million-Year-Old Fossil Alters Octopus Evolution Timeline
A fossil previously identified as the oldest known octopus has been reclassified as a different marine animal, challenging long-held assumptions about cephalopod evolution. The fossil, Pohlsepia mazonensis, discovered at the Mazon Creek site in Illinois, was initially described in 2000 as a cirrate octopod, suggesting an earlier origin for octopuses by 150 million years. However, new research using synchrotron micro-X-ray fluorescence imaging revealed a radula, a feeding organ with teeth, indicating it is a nautiloid relative, not an octopus. This reclassification impacts molecular clock studies that used the fossil as a calibration point, now supporting a Jurassic period divergence for crown octopuses. 
