Creature thought to be world's oldest octopus isn't an octopus after all

A team of international paleontologists has definitively reclassified a 300-million-year-old fossil, discovered in Montana, USA, from being considered the world's oldest known octopus to a relative of the nautilus, based on new analysis of its shell structure published in a leading scientific journal this week. The correction resolves a decades-long paleontological mystery and significantly reshapes the evolutionary timeline for cephalopods, the class of mollusks that includes octopuses, squid, and cuttlefish. The fossil, named *Syllipsimopodi bideni* when it was first described in 2022, was celebrated for its apparent preservation of ten arms and two fins, features aligning it with modern vampire squid and octopuses. This classification pushed back the origin of octopuses by over 80 million years. However, a meticulous re-examination using advanced imaging techniques revealed critical details previously missed. Researchers identified a robust, chambered internal shell, a hallmark of nautiloids, rather than the reduced or absent shell characteristic of octopuses and their close relatives (coleoids). This discovery underscores the challenges of interpreting ancient, often incomplete fossils and the revolutionary role of modern technology in paleontology. It corrects the creature's place on the evolutionary tree, placing it within the nautiloid lineage that thrived in the ancient oceans of the Carboniferous period. Consequently, the title of 'oldest octopus' reverts to a 240-million-year-old fossil from Germany, preserving the previously understood chronology of when soft-bodied, shell-less cephalopods like octopuses first emerged. The study highlights how scientific understanding is provisional and evolves with new evidence, even for fossils that seem to tell a clear story.