Reevaluation Reveals 'Oldest Octopus' Fossil Is a Nautilus Relative

A 300-million-year-old fossil, once celebrated as the world's oldest octopus, has been reclassified as a relative of modern nautiluses following advanced imaging analysis. The specimen, Pohlsepia mazonensis, was discovered in Illinois and had been featured in the Guinness Book of Records as the earliest known octopus.

Researchers from the University of Reading utilized synchrotron imaging to examine the fossil's internal structure. This technique revealed the presence of a radula—a ribbon-like tongue with rows of microscopic teeth—characteristic of nautiloids but distinct from octopuses. Dr. Thomas Clements, the study's lead author, noted that the fossil's soft tissues had decomposed before fossilization, leading to its initial misidentification.

The reclassification of Pohlsepia mazonensis as a nautiloid suggests that octopuses likely evolved during the Jurassic period, approximately 150 million years later than previously believed. This finding also extends the record of nautiloid soft tissue preservation by about 220 million years.

The fossil is housed at the Field Museum of Natural History in Chicago. Paul Mayer, the museum's invertebrate fossil collections manager, expressed surprise at the reclassification but acknowledged that the specimen's classification had been debated since its initial description in 2000.