The fossil known as Pohlsepia mazonensis, previously hailed as the oldest known octopus, has been reclassified following advanced imaging tests conducted by Thomas Clements, a paleontologist at the University of Leicester, and his team. Dating back to the late Carboniferous period, approximately 311 to 306 million years ago, this specimen was long considered an anomaly in cephalopod evolution, as it suggested that crown coleoids, which include octopuses, diverged much earlier than the Jurassic period. However, the latest research revealed that Pohlsepia is not an octopus but a decomposed nautiloid. The misidentification stemmed from the unique fossilization process at the Mazon Creek Lagerstätte in Illinois, where organisms were preserved in iron-rich sediment, resulting in flat, two-dimensional impressions that made it difficult for early paleontologists to accurately interpret their anatomy. This finding significantly impacts the understanding of cephalopod evolution, indicating that true octopuses emerged much later than previously believed.