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Ancient Fossil Reclassified as Oldest Soft-Tissue Nautilus

4/13/2026

Summary

Story summary

Researchers reclassified the fossil Pohlsepia mazonensis, a 300-million-year-old specimen from Illinois housed at the Field Museum in Chicago, from the oldest octopus to a nautilus.
Researchers led by Thomas Clements of the University of Reading reclassified it after examining its teeth.
The teeth show more than octopus teeth, supporting nautilus identification.
The fossil is now the oldest soft-tissue nautilus.
The next oldest octopus fossil is about 90 million years younger.

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Story summary

Researchers reclassified the fossil Pohlsepia mazonensis, a 300-million-year-old specimen from Illinois housed at the Field Museum in Chicago, from the oldest octopus to a nautilus.
Researchers led by Thomas Clements of the University of Reading reclassified it after examining its teeth.
The teeth show more than octopus teeth, supporting nautilus identification.
The fossil is now the oldest soft-tissue nautilus.
The next oldest octopus fossil is about 90 million years younger.