A FAMOUS 300-million-year-old fossil thought to be the world’s oldest octopus has turned out to be something else altogether following research led by a University of Reading lecturer.
The specimen was found in Illinois, USA, and the first analysis led researchers to believe it was an octopus fossil.
Its apparent showing of eight limbs and fins, as well as other similar characteristics associated with the octopus.
The discovery pushed back the known history of the animal to around 150 million years earlier than it had thought, and even featured in the Guinness Book of Records after the research was published at the turn of the millenium.
However doubts had been raised about the identification–doubts which were explored in the new study using a cutting-edge technology: synchrotron imaging.
Researchers used beams of light brighter than the sun to scan for sub-surface structures and deeper details, in a process described as similar to modern forensic examination.
What they found was a ‘radula’, a ribbon-like feeding structure with rows of teeth only found in molluscs.
With at least 11 tooth-like elements per row, the shape and number ruled out an octopus entirely; octopuses have seven or nine, while nautiloids have 13.
As such, scientists now believe that the fossil is that of a nautilus, now thought to be the oldest known nautiloid soft tissue in the fossil record, itself beating the previous record by around 220 million years.
These findings change the picture of when octopuses first evolved–the data now supports octopuses appearing much later, during the Jurassic period.
It is now believed that the split between octopuses and their ten-armed relatives such as squids happened in the Mesozoic era, not hundreds of millions of years earlier as previously thought.
Dr Thomas Clements, lead author and Lecturer in Invertebrate Zoology at the University of Reading, said: “It turns out the world’s most famous octopus fossil was never an octopus at all. 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.
“Scientists identified Pohlsepia as an octopus 25 years ago, but using modern techniques showed us what was beneath the surface to the rock, which finally cracked the case.
“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.
“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.”
