The “world’s oldest octopus” was truly a 300-million-year-old fossil impostor hiding its secret in tiny tooth.
A fossil lengthy celebrated because the world’s oldest octopus has now been revealed to be a completely completely different marine animal. The 300-million-year-old specimen, which even appeared within the Guinness Ebook of Data, was misidentified due to adjustments that occurred to the animal’s physique earlier than it grew to become fossilized.
Researchers found that the fossil, often called Pohlsepia mazonensis, was not an octopus in any respect. As an alternative, it belonged to a gaggle associated to the trendy Nautilus, a shelled sea creature with many tentacles.
The breakthrough got here after scientists used superior synchrotron imaging to look at hidden constructions contained in the fossil rock. Their scans uncovered tiny preserved tooth that uncovered the fossil’s true id.
The findings have been revealed in Proceedings of the Royal Society B. The examine resolves a decades-long thriller surrounding octopus evolution and likewise supplies the oldest identified instance of preserved nautiloid smooth tissue ever found. In consequence, the fossil’s title because the world’s “oldest octopus” is now not legitimate.
Hidden Tooth Clear up a A long time-Lengthy Thriller
Dr. Thomas Clements, lead writer and Lecturer in Invertebrate Zoology on the College of Studying, stated: “It seems the world’s most well-known octopus fossil was by no means an octopus in any respect. It was a nautilus relative that had been decomposing for weeks earlier than it grew to become buried and later preserved in rock, and that decomposition is what made it look so convincingly octopus-like.
“Scientists recognized Pohlsepia as an octopus 25 years in the past, however utilizing fashionable strategies confirmed us what was beneath the floor to the rock, which lastly cracked the case. We now have the oldest smooth tissue proof of a nautiloid ever discovered, and a a lot clearer image of when octopuses truly first appeared on Earth.
“Generally, reexamining controversial fossils with new strategies reveals tiny clues that result in actually thrilling discoveries.”
Fossil Scans Reveal New Particulars
The fossil was found in Illinois, USA, and first described in a scientific examine in 2000. Researchers initially believed the specimen displayed eight arms, fins, and different octopus-like options. That interpretation recommended octopuses existed roughly 150 million years sooner than scientists had beforehand thought.
Through the years, some paleontologists questioned whether or not the fossil had been appropriately recognized, however there was no dependable option to verify these doubts till now.
Within the new analysis, scientists used synchrotron imaging, a way that depends on beams of sunshine brighter than the solar to detect constructions hidden inside rock. The crew in contrast the method to finishing up a contemporary forensic investigation on a fossil that’s 300 million years outdated.
Historical Nautiloid Mistaken for Octopus
The scans revealed a radula, a ribbon-like feeding construction lined with rows of tooth that’s distinctive to mollusks. The quantity and association of these tooth instantly dominated out an octopus.
Researchers discovered a minimum of 11 tooth-like constructions in every row. Octopuses sometimes have seven or 9 tooth per row, whereas nautiloids have 13.
The tooth carefully matched these of Paleocadmus pohli, a fossil nautiloid species already known from the same Illinois fossil site. Scientists concluded the animal had partially decomposed before fossilization, dramatically altering its appearance and making it resemble an octopus.
Octopus Evolution Timeline Changes
The Nautilus, which still exists today, is often called a “living fossil” because its lineage stretches far back into Earth’s history. The Paleocadmus fossils from the Mazon Creek site in Illinois now represent the oldest known preservation of nautiloid soft tissue in the fossil record, surpassing the previous record by about 220 million years.
The discovery also changes scientists’ understanding of when octopuses first evolved. Current evidence now points to octopuses appearing later, during the Jurassic period.
Researchers also now believe the evolutionary split between octopuses and their ten-armed relatives, including squids, occurred during the Mesozoic era rather than hundreds of millions of years earlier.
Dr. Clements said: “It’s amazing to think a row of tiny hidden teeth, hidden in the rock for 300 million years, have fundamentally changed what we know about when and how octopuses evolved.”
Reference: “Synchrotron data reveal nautiloid characters in Pohlsepia mazonensis, refuting a Palaeozoic origin for octobrachians” by Thomas Clements, Imran Alexander Rahman, Alan R. T. Spencer, Christian Klug, Dirk Fuchs, Isabelle Rouget, Isabelle Kruta, Sebastian Schöder, Jack Wittry, Orla G. Bath Enright and Pierre Gueriau, 8 April 2026, Proceedings of the Royal Society B Biological Sciences.
DOI: 10.1098/rspb.2025.2369
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