Palaeontology

World's earliest known octopus turns out to be something else entirely

By T.K. Randall
April 9, 2026

Image: Nautilus from the side, Palau, Micronesia
Credit: Profberger / CC BY-SA 3.0 (adapted) Originally discovered at Mazon Creek in Illinois several decades ago, the fossil - which dates back 300 million years - was believed to be something very special when it was excavated and examined.

Upon closer inspection, scientists found evidence of eight tentacles and other signs that this was in fact an octopus - the earliest example of its kind found anywhere in the world.

Now, however, a new analysis using modern techniques has revealed that the fossil is not an octopus, but a nautilus - a type of multi-tentacled sea creature with a shell.

It turned out that the reason the fossil resembled that of an octopus was because the creature must have decomposed for several weeks before being preserved.It wasn't until modern imaging technology revealed what lay beneath the surface of the rock that it became clear what the creature actually was.

"It turns out the world's most famous octopus fossil was never an octopus at all," said lead study author Dr Thomas Clements of the University of Reading.

"It was a nautilus relative that had been decomposing for weeks before it became buried and later preserved in rock, and that decomposition is what made it look so convincingly octopus-like."

"We now have the oldest soft tissue evidence of a nautiloid ever found, and a much clearer picture of when octopuses actually first appeared on Earth."

"Sometimes, reexamining controversial fossils with new techniques reveals tiny clues that lead to really exciting discoveries."

Source: BBC News

Tags: Octopus, Fossil