Scientists have found fossil evidence suggesting giant octopuses lived about 100 million years ago, pushing the animals’ history deep into the Cretaceous seas. The study, published in Science, revisits 15 large fossil jaws from Hokkaido Island in northern Japan and concludes they belonged to two extinct octopus species.
Palaeontologists from Hokkaido University used digital fossil mining to re-examine the jaws, which had first been identified as belonging to early octopus relatives. The technique grinds away a super-thin layer of the fossil-bearing rock, photographs each surface in high resolution, and repeats the process thousands of times to build a 3D, full-colour model. That work pointed to Nanaimoteuthis jeletzkyi and N. haggarti, and to animals far larger than modern octopuses.
One of the species, N. haggarti, may have measured between 7 and 19 metres in total length, including long arms, with a body length of about 1.5 to 4.5 metres. Researchers said the animals had powerful arms for grabbing prey and beak-like jaws for crushing shells and bones. They also found extensive wear on the jaws, which suggests the octopuses crunched hard shells and bones, and uneven wear from left to right that may mean they favoured one side when feeding.
Yasuhiro Iba described the animals as “huge, intelligent,” a fitting label for creatures that appear to have hunted with strength and precision in seas long thought to be ruled by sharks and giant marine reptiles. Christian Klug said, “With their tentacles and their suckers they could perfectly hold on to such an animal and there is no escape,” a line that helps explain how the predators may have handled prey such as 11-metre-long mosasaurs and 12-metre-long plesiosaurs.
The fossil record for soft-bodied octopuses and squids is usually thin, because their bodies do not preserve well and their chitinous beaks are often the main traces left behind. That is why the Hokkaido jaws matter now: they place octopuses among the largest invertebrates ever described, and they show that the animals’ evolutionary story was already large and complex in the Cretaceous ocean. Shin Ikegami said, “This laterality is related to the complexity of the brain,” suggesting the feeding wear may reflect a one-sided preference linked to behaviour seen in modern octopuses.
Modern octopuses are already known for problem solving, learning and complex hunting strategies, and the Giant Pacific Octopus, the largest living species today, can have an arm span of more than 5.5 metres. The new fossils do not just add size to that picture. They show that giant octopuses were not a late evolutionary surprise, but an ancient presence in the sea — and likely one of the biggest invertebrate predators of their time.
