The 'world's oldest octopus' fossil isn't actually an octopus

Embargoed until: Publicly released: 2026-04-08 09:01

International

Reconstruction of a Paleocadmus decaying. Clements, T. et al. / Royal Society

Pohlsepia mazonensis, a famous 300-million-year-old fossil long thought to be the world's oldest octopus – even featuring in the Guinness Book of Records – isn't an octopus at all, according to international scientists. The team used the latest synchrotron imaging techniques to search inside the fossil, finding tiny teeth preserved inside the rock which prove that P. mazonensis is not an octopus, but an animal related to a modern Nautilus – a multi-tentacled critter with an external shell. The scientists say the creature that gave rise to the fossil decomposed for weeks before it was preserved, and that decomposition is what made it look octopus-like. The findings solve a long-running puzzle in octopus evolution that has confused scientists for decades, the researchers say, and suggest octopuses probably evolved hundreds of millions of years later than we thought.

News release

From: The Royal Society

Synchrotron data reveal nautiloid-characters in Pohlsepia mazonensis, refuting a Palaeozoic origin for octobrachians

A 300-million-year-old fossil once hailed as the world's oldest octopus—even featured in the Guinness Book of Records—has been dramatically reclassified. Using advanced synchrotron imaging to look inside the fossil, researchers discovered that Pohlsepia mazonensis is actually related to modern Nautilus, not octopuses. The organism had decayed significantly before fossilization, obscuring its true identity for decades. The finding resolves a long-standing puzzle in octopus evolution and reveals the oldest preserved nautiloid soft tissue ever found.

Noctopus - The 300-million-year-old fossil featured in the Guinness Book of Records as the world's oldest octopus has been dramatically reclassified. Using synchrotron imaging to produce 3D images of the fossil, researchers found a previously undetected radula – the toothed tongue found in most molluscs. The shape of the radula suggests the fossil belongs to the shelled nautiloids. The finding resolves a long-standing puzzle in octopus evolution and reveals the oldest preserved nautiloid soft tissue ever found.*Noctopus - The 300-million-year-old fossil featured in the Guinness Book of Records as the world's oldest octopus has been dramatically reclassified. Using synchrotron imaging to produce 3D images of the fossil, researchers found a previously undetected radula – the toothed tongue found in most molluscs. The shape of the radula suggests the fossil belongs to the shelled nautiloids. The finding resolves a long-standing puzzle in octopus evolution and reveals the oldest preserved nautiloid soft tissue ever found.