Share to ClassroomGiant Octopuses Once Hunted Among the Dinosaurs
Scientists have uncovered fossil evidence suggesting that the ancestors of modern octopuses were gigantic predators that prowled the oceans alongside dinosaurs around 100 million years ago. According to research published in the journal Science by a team from Hokkaido University in Japan, fossilised jaws preserved in Late Cretaceous rock samples indicate that some of these ancient cephalopods grew to nearly 20 metres in length, rivalling and even surpassing the largest marine reptiles of their era. The specimens were recovered from seafloor sediments in Japan and on Vancouver Island, dating from between 100 and 72 million years ago, and they dramatically rewrite the timeline of finned octopus evolution.
Until now, the earliest known finned octopuses were thought to have lived only about 15 million years ago. Because octopuses are soft-bodied animals, their evolutionary history has been notoriously difficult to trace, since only the hard jaw bones tend to survive as fossils. To overcome this obstacle, the Hokkaido team, led by Professor Yasuhiro Iba, used a technique called high-resolution grinding tomography, combined with an artificial intelligence model, to detect the tiny structures hidden inside the rock. The fossilised jaws belong to an extinct group known as Cirrata, whose powerful biting apparatus could crush hard-shelled prey. Dr Nick Longrich, a palaeontologist at the University of Bath, suspects the giants mainly hunted ammonites, though he cautioned that scientists are still piecing the picture together.
Perhaps the most striking finding concerned the wear marks on the jaws themselves. According to Iba, in well-grown specimens up to ten per cent of the jaw tip showed chipping, scratching and cracking, greater wear than is seen in any modern cephalopod that feeds on hard-shelled creatures. This pattern points to an unexpectedly aggressive feeding strategy involving repeated, forceful encounters with prey. The researchers argue that their discovery overturns long-held assumptions that vertebrates alone occupied the top of the Cretaceous food chain. As Iba put it, the study provides the first direct evidence that invertebrates can evolve into intelligent, apex predators, opening fresh questions about how marine ecosystems were structured in the age of dinosaurs.
