The ‘oldest octopus’ in the world isn’t an octopus after all, scientists find

Reconstruction of a Paleocadmus decaying prior to burial in the Mazon Creek marine basin. (Franz Anthony/ Proceedings of the Royal Society B)

The story of a 300-million-year-old fossil has been rewritten after scientists discovered that it doesn’t actually belong to the world’s oldest octopus as previously thought.

In fact, it belongs to an animal related to a modern nautilus, which has tentacles and an external shell, according to a study published Wednesday in the journal Proceedings of the Royal Society B.

“We basically used a wide selection of new analytical techniques to discover hidden anatomical characteristics within the rock,” lead study author Thomas Clements, a lecturer in invertebrate zoology at the University of Reading, England, told CNN on Thursday.

“And we were able to determine that it is not an octopus, but is actually a very decomposed nautiloid, which is a relative of modern nautiluses.”

The fossil, named Pohlsepia mazonensis, was found at the Mazon Creek site just south of Chicago, Illinois.

Paleontologists had long been puzzled by the fossil as it is far older than the next oldest known octopus, which dates back about 90 million years.

Clements explained that the animal had been decomposing for weeks before it was buried, giving its fossil an octopus-like appearance that led many scientists to conclude that octopuses had lived far earlier than previously thought.

However, others questioned whether this was in fact the case, as certain features such as the length and shape of its arms didn’t match what would be expected, said Clements.

Mistaken identity

As a result, he decided to reexamine the fossil using new scientific techniques that weren’t available when the first analysis of it was published in 2000.

“We used a huge selection of new techniques,” he said, including using a scanning electron microscrope and carrying out geochemistry work.

But still the fossil refused to reveal its true identity.

“We weren’t getting anywhere,” said Clements. “I was quite frustrated.”

Things changed when a colleague invited him to scan the fossil using synchrotron imaging, a technique described by the University of Reading as using beams of light brighter than the sun. This technique “generates the world’s most powerful X-rays,” Clements explained.

“It revealed anatomical characters that were hidden just below the surface of the rock, so you can’t visually see it when you’re looking at the fossil,” said Clements.

The team had found a radula, a feeding structure with rows of teeth. There were at least 11 per row in the fossil, whereas octopuses only have seven or nine, according to a statement from the University of Reading.

“It was these tiny teeth that we found that allowed us to identify that it wasn’t an octopus,” he added.

Clements said that the research demonstrates the power of new technologies to advance our scientific understanding.

“Not only are they becoming more readily available but they’re becoming more affordable, and that’s revolutionizing paleontological investigations,” he said, highlighting the use of synchotrons to discover ancient proteins and biomolecules, and engineering techniques originally designed to test building materials to work out the strength of a dinosaur bite.

“A lot of people think of paleontology as a very dusty science,” said Clements. “But actually, we’re an incredibly innovative science.”