Oldest octopus fossil found to not be an octopus

A fossil celebrated as the earliest known octopus is now identified as a different, more ancient cephalopod, rewriting a key chapter in evolutionary history. | Contesto: cronaca

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• Oldest octopus fossil found to not be an octopus

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A fossil specimen, celebrated for over a decade as the oldest known ancestor of the modern octopus, has been conclusively reclassified as a different and more ancient type of cephalopod. The groundbreaking reassessment, published in a detailed paleontological study, dismantles a long-held assumption about the origins of these intelligent, eight-armed creatures. The fossil, discovered in Montana's Bear Gulch Limestone formation and dating to approximately 330 million years ago, was originally named Pohlsepia mazonensis and heralded as a revolutionary find that pushed back the octopus lineage by tens of millions of years. The initial classification was based on the fossil's distinct, octopus-like silhouette, complete with eight arms and what appeared to be an ink sac. This interpretation placed Pohlsepia firmly within the octopus lineage, or Octopodiformes, suggesting these animals evolved much earlier in the Carboniferous period than previously thought. The discovery challenged established evolutionary timelines and was widely cited in scientific literature and popular science as a pivotal "first." However, the fossil's preservation in two dimensions and its unusual, rounded body shape had always left room for doubt among specialists, prompting the new, rigorous investigation. Led by an international team of paleontologists, the re-examination employed advanced imaging techniques and a comparative analysis with other ancient cephalopods. The researchers determined that key anatomical features were misinterpreted. The structure identified as an ink sac is likely a fragment of the animal's body cavity, and the overall body plan does not align with the internal musculature and morphology expected in a true octopus. Instead, the evidence points to Pohlsepia being a member of the vampyropods, a group that includes the vampire squid and is considered a sister lineage to both octopuses and squid. This group is itself ancient, but Pohlsepia represents a unique, early branch with a convergent, octopus-like appearance. "This is a classic case of convergent evolution, where two unrelated groups develop similar shapes," explained Dr. Anne K. Landman, a co-author of the...

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Categoria: cronaca