LONDON (AP) 鈥� A 300-million-year-old tentacled sea creature has lost its crown as the world鈥檚 oldest octopus, after scientists found evidence that it鈥檚 not an octopus at all.
Newly published research concludes that fossilized remains listed by Guinness World Records as the earliest known octopus belong instead to a relative of a nautilus, a cephalopod with both tentacles and a shell.
University of Reading zoologist Thomas Clements, the lead researcher behind the new findings, said the fossil, Pohlsepia mazonensis, has long been the subject of scientific debate.
鈥淚t鈥檚 a very difficult fossil to interpret,鈥� he said. 鈥淭o look at it, it kind of just looks like a white mush.
鈥淚f you look at it and you are a cephalopod researcher and you鈥檙e interested in everything octopus, it does superficially look a lot like a deep-water octopus.鈥�
The creature, a blob about the size of a human hand, was found in the Mazon Creek area of Illinois, about 50 miles southwest of Chicago, that is rich in fossils from a period before dinosaurs walked the Earth.
Its identification by paleontologists as an octopus in 2000 upended ideas about the , suggesting they emerged much earlier than previously thought. The next oldest-known octopus fossil is only about 90 million years old.
鈥淚t鈥檚 a huge gap,鈥� Clements said. 鈥淎nd so that big gap got researchers sort of questioning, 鈥業s this thing actually an octopus?鈥�
To solve the mystery of the 鈥渨eird blob,鈥� Clements and his team used a synchrotron 鈥� which uses fast-moving electrons to create beams of light brighter than the sun 鈥� to look inside the fossil rock. They found a ribbon of teeth known as a radula that is common to all mollusks, including nautiluses and octopuses. Each row had 11 teeth. Octopuses have either seven or nine.
鈥淭his has too many teeth, so it can鈥檛 be an octopus,鈥� Clements said. 鈥淎nd that鈥檚 how we realize that the world鈥檚 oldest octopus is actually a fossil nautilus, not an octopus.鈥�
The teeth matched those of a fossil nautiloid called Paleocadmus pohli that had been found in the same area. Clements said the mistaken identification may have happened because the creature decomposed and lost its telltale shell before it was fossilized, complicating identification.
As a result of the findings published this week in the journal Proceedings of the Royal Society B, Guinness World Records said it will no longer list Pohlsepia mazonensis as the earliest known octopus.
Managing Editor Adam Millward said the scientists had made 鈥渁 fascinating discovery.鈥�
鈥淲e will be resting the original 鈥榦ldest octopus fossil鈥� title and look forward to reviewing this new evidence,鈥� he said.
Pohlsepia mazonensis is named for its discoverer James Pohl, and is in the collection of the Field Museum in Chicago.
Paul Mayer, manager of the museum’s collection of fossil invertebrates, said he was 鈥渁 little surprised鈥� by its new classification as a nautiloid, but noted that “people have been questioning whether it was an octopus ever since the original paper was first published in 2000.鈥�
He said new technologies for scientific investigation had brought renewed interest in the Mazon Creek fossils.
鈥�(That) is great for our collections and hopefully new discoveries will be made and new stories will be revealed,鈥� Mayer said.
Clements said the museum should not be disappointed by the new evidence, which means it now has 鈥渢he oldest soft tissue nautilus in the world.
鈥淭he Field Museum have a small collection of these ancient nautiluses, which I think as a cephalopod worker is probably the best thing ever,鈥� he said.
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