Today's octopuses are intelligent, remarkably flexible animals that lurk in reefs, hide in crevices, or drift through the deep sea. But new research suggests that their earliest relatives may have played a far more predatory role in ocean ecosystems. A study led by researchers at Hokkaido University has found that the earliest known octopuses were giant predators that hunted at the very top of the food web, alongside large marine vertebrates. The study is published in Science.

Fossil jaws reveal hidden history
Octopuses are soft-bodied animals, and they rarely fossilize well. This makes their evolutionary history especially difficult to trace compared with animals that leave behind bones or shells. In this study, the researchers used fossil jaws of early octopuses, a feeding organ with a high fossilization potential, to reconstruct their hidden history.

Using high-resolution grinding tomography and an artificial intelligence model, they found fossil jaws hidden inside rock samples from the Late Cretaceous period, spanning 100 million to 72 million years ago. These fossils, found in Japan and Vancouver Island, had been well preserved in calm seafloor sediments, retaining fine wear marks that revealed how these animals fed.

The fossils belonged to a group of extinct finned octopuses, known as Cirrata. By analyzing the size, shape, and wear patterns of the jaws, the team concluded that these animals were active predators that likely crushed hard prey with powerful bites.