Scientists have discovered that giant octopuses up to 19m (62ft) long were the true apex predators of the dinosaur-age oceans.
Publishing their findings in the journal Science, researchers analysed fossilised jaws from two species of finned octopus, Nanaimoteuthis jeletzkyi and N. haggarti, recovered from Late Cretaceous sediments dating to between 100 and 72 million years ago.
Extensive wear on the jaws of adult specimens revealed these creatures were powerful, active carnivores that routinely crushed hard shells and bones. The largest of these octopuses rivalled even the biggest marine reptiles of their age in size.
“They lived in the oceans of the dinosaur age, alongside marine reptiles, large fish, sharks, ammonites and large shell-bearing animals,” lead author Yasuhiro Iba, an associate professor at Hokkaido University in Japan, told BBC Science Focus.
“Nanaimoteuthis likely used its large body and long arms to capture prey, and its powerful jaws to crush shells and bones. It was not just large – it was an active, intelligent predator operating at the very top of the marine food web.”
The team used a technique called digital fossil-mining – converting rock interiors into high-resolution image datasets and using AI to extract 3D fossil models – to uncover 12 previously hidden octopus jaws.
According to Iba, this method can increase fossil discovery rates by more than 10,000 times over traditional approaches.
Asymmetric wear on the jaws suggested the creatures showed a preference for one side, akin to left or right handedness. This, the researchers said, may indicate that these ancient giants were highly intelligent, given such lateralised behaviour is consistent with the modern octopuses who often have a preference of arms and eyes.
The creatures may represent the largest invertebrates ever described, with Iba's team nicknaming them the “Cretaceous Kraken”.
As for what happened to them: their descendants now lurk in the deep sea, long since displaced by a new generation of apex predators.
“They were probably overtaken by modern-type predators, such as whales,” Iba said.
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