Topic: Biology

Scientists reexamined a 300-million-year-old fossil and found it was not an octopus after all. Instead, it belongs to a group related to modern Nautilus.

The world's oldest octopus fossil, once believed to be the oldest of its kind, has been reclassified. This 300-million-year-old specimen had even earned a place in the Guinness Book of Records, but scientists now say that distinction was based on a misinterpretation.

The confusion traces back to events that happened long before the fossil formed. As the animal decayed hundreds of millions of years ago, its body changed in ways that later made it resemble an octopus when preserved in rock.

Advanced Imaging Reveals Hidden Teeth Researchers used cutting-edge synchrotron imaging to examine the inside of the fossil in detail. This powerful technique allowed them to detect tiny structures that cannot be seen with the naked eye.

Inside the rock, they found small tooth-like features that changed everything. The fossil, known as Pohlsepia mazonensis, is not an octopus. Instead, it belongs to a group related to modern Nautilus, marine animals that have multiple tentacles and a distinctive external shell.

The findings, published in Proceedings of the Royal Society B, resolve a long-standing mystery about octopus evolution that has puzzled scientists for decades.

Reexamining a Fossil From Illinois The fossil was originally discovered in Illinois, USA, and first described in 2000. It quickly became important in studies of cephalopod evolution, with scientists interpreting its features as evidence of eight arms, fins, and other traits associated with octopuses.

This pushed the known origin of octopuses back by about 150 million years. Over time, some researchers questioned this interpretation, but there was no reliable way to investigate further until recently.

Fossil Teeth Reveal Nautiloid Identity The scans uncovered a radula, a ribbon-like feeding organ lined with rows of tiny teeth that is found in molluscs. The number and arrangement of these teeth provided a crucial clue.

The fossil showed at least 11 tooth-like structures per row, which does not match octopuses, which have seven or nine. Nautiloids, in contrast, typically have 13.

The teeth closely matched those of a known fossil nautiloid species, Paleocadmus pohli, which has been found at the same site.

Based on this evidence, the researchers concluded that the animal had partially decomposed before fossilization, altering its appearance and leading to the earlier misidentification.

New Timeline for Octopus Evolution

Why It Matters

This discovery helps us better understand how octopuses evolved over time. It also shows how advanced imaging techniques can be used to resolve long-standing mysteries in science.

Key Facts

• The fossil, Pohlsepia mazonensis, is 300 million years old and was previously thought to be the oldest octopus fossil.
• Advanced synchrotron imaging revealed that the fossil is actually a nautiloid, not an octopus.
• The discovery provides new insights into the evolution of octopuses and resolves a long-standing mystery in science.
• The fossil's teeth closely matched those of a known fossil nautiloid species, Paleocadmus pohli.
• The researchers used advanced imaging techniques to detect tiny structures that cannot be seen with the naked eye.

Key Terms

Synchrotron Imaging

A powerful technique that uses extremely bright beams of light to detect hidden structures within rock.

Implications

This discovery helps us better understand how octopuses evolved over time. It also shows how advanced imaging techniques can be used to resolve long-standing mysteries in science.