Museum display found to be entirely new species after 26 years: 'Difficult to decipher'

Key Points:

• The 300-million-year-old fossil Pohlsepia mazonensis, once believed to be the oldest-known octopus, has been reclassified as a nautilus after high-powered X-ray scans revealed a radula inconsistent with octopus anatomy.
• The fossil's original classification challenged the timeline of octopus evolution by suggesting the genus appeared 150 million years earlier than previously thought, but this conflicted with established research based on other fossil samples.
• Researchers found that the fossil's soft tissues were ambiguous due to partial decomposition before fossilization, which complicated its initial identification as an octopus.
• The new findings support that octopuses likely evolved during the Jurassic period, after diverging from other cephalopods like squids, and highlight the rarity of fossilized nautilus remains despite their long evolutionary history.
• The re-examination of Pohlsepia mazonensis reflects broader efforts to apply advanced technology to ancient fossils, with ongoing studies of other enigmatic specimens from the Mazon Creek fossil site, such as the Tully Monster.