A fossil that researchers had long believed to be the world's oldest octopus has been reclassified as an ancient relative of the nautilus, according to a new study.

The 300-million-year-old specimen had been previously identified as an early octopus, which would have made it the oldest known fossil of its kind. However, researchers now say the creature was actually related to nautiluses, a group of marine mollusks that still exist today.

The reclassification represents a significant correction in paleontological understanding of ancient marine life. Nautiluses are cephalopods like octopuses, but they belong to a different evolutionary branch and are characterized by their distinctive spiral shells.

The study highlights the ongoing challenges paleontologists face when interpreting ancient fossils, particularly when dealing with soft-bodied creatures that rarely preserve well in the fossil record. Such corrections are common in paleontology as new analytical techniques and comparative studies provide better understanding of ancient specimens.

The findings contribute to scientists' broader understanding of how cephalopods evolved over hundreds of millions of years and diversified into the various species seen today, including octopuses, squid, cuttlefish, and nautiluses.