A fossil known as Pohlsepia mazonensis, previously labeled as the world's oldest octopus, has been reclassified as a nautiloid, a type of shelled cephalopod related to modern Nautilus species. Discovered in Illinois, the fossil was initially thought to be an octopus due to its eight arms and fin-like structures. However, recent research employing advanced synchrotron imaging revealed a row of tiny tooth-like structures known as a radula, characteristic of molluscs. The radula contained 11 tooth-like elements per row, aligning with nautiloids, while octopuses typically have seven or nine. Dr. Thomas Clements, the lead author and a 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.” This reclassification not only resolves a long-standing puzzle in octopus evolution but also suggests that octopuses evolved much later than previously thought, likely during the Jurassic period. The study underscores the significance of utilizing modern techniques to revisit and reassess controversial fossils, leading to groundbreaking discoveries.