At the time of the dinosaurs, the oceans were teeming with life. Below the waves, giant marine reptiles, such as the fearsome 4m (13ft) long mosasaurs, were the undisputed apex predators.

In artistic reconstructions of these ancient oceans, cephalopods – the animal group that includes squid, cuttlefish, octopuses, and their ancestors – are almost always portrayed as prey, often seen desperately swimming away from the jaws of a marine reptile to avoid becoming lunch.

However, a remarkable new fossil suggests our view of the ancient oceans is incomplete, and that giant octopuses, perhaps reaching as long as 19m (62ft), may have been the ones doing the hunting.

The fossil in question is a giant octopus jaw, belonging to a new species called Nanaimoteuthis haggarti. It is found in Late Cretaceous rocks of Japan, making it between 100 million and 72 million years old.

Like other cephalopods, octopuses have a hard beak that looks like a parrot’s bill, used to bite and tear prey, and this fossil example is enormous – larger than that of the famous giant squid Architeuthis.

Based on the shape and size of the beak, Shin Ikegami, from........

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