For centuries, the kraken was a creature of human imagination, the giant octopus that would coil around ships and drag them to the bottom of the sea to devour their sailors, according to legend. A study published this Thursday in the journal Science demonstrates that the legend had an astonishing paleontological basis: in the oceans of the Late Cretaceous, between 100 and 72 million years ago, there existed giant octopuses that could reach 19 meters in length, were carnivorous, and occupied the top of the food chain, competing with the large marine reptiles that until now were considered the sole rulers of those seas.
The scientific team that made this discovery, led by Shin Ikegami of Hokkaido University (Japan), identified two extinct cephalopod species—Nanaimoteuthis jeletzkyi and N. haggarti—from the analysis of 27 fossilized beaks recovered from marine sediments in Japan and Vancouver Island, Canada. The larger species, N. haggarti, would have reached between 7 and 19 meters in total length, figures that place it among the largest invertebrates ever described in the fossil record, and put it on par with mosasaurs, the gigantic marine reptiles of the Cretaceous period, and plesiosaurs.
Octopuses have always been very difficult to study in the fossil record because they are invertebrates. Unlike dinosaurs, they don’t leave bones behind, and unlike ammonites, they don’t leave shells. What does endure are their jaws, hard structures that scientists call “beaks” because of their resemblance to those of birds of prey. And these beaks, when well preserved, tell many stories: they not only allow us to estimate the size of the animal, but also what it ate. The wear on the beak is key to the study. Cephalopods that feed on hard-shelled prey—crustaceans, mollusks, bony fish—develop characteristic wear on the edge and tip of the beak, which erodes with repeated use. It’s the same principle as a knife sharpened against stones: the tool retains the memory of its use.
In adult specimens of Nanaimoteuthis, wear removed up to 10% of the total beak length, more than in any known modern cephalopod, suggesting intense and sustained predatory activity throughout the animal’s life.
Regarding the reliability of these estimates, Ikegami is cautious but firm: “N. haggarti was comparable in size to the modern giant squid, and many estimates exceed it. The conclusion that it was among the largest invertebrates in Earth’s history is robust,” the researcher states.
Furthermore, there is an even more revealing detail: the wear is not symmetrical. The right edge of the jaw appears more worn than the left in both species. This lateralization, that is, the tendency to preferentially use one side of the body, is associated in modern animals with more developed brains and more complex cognitive behaviors. Modern octopuses exhibit this trait, and their intelligence, documented in numerous studies, is comparable to that of many vertebrates. The finding suggests that octopuses were already intelligent animals 100 million years ago.
Specifically, the Late Cretaceous, between 100 and 66 million years ago, is the period that ended with the massive impact that wiped out the dinosaurs. It was a world of warm, shallow seas that covered vast areas of what are now the continents. According to scientific consensus, these seas were ruled by large vertebrates: mosasaurs up to 17 meters long, plesiosaurs up to 12 meters, and shell-crushing sharks like Ptychodus, up to 10 meters long. Invertebrates were, in this narrative, the victims; organisms that developed increasingly thick and elaborate shells as an evolutionary response to the predatory pressure of vertebrates.
The new study turns that narrative on its head. Nanaimoteuthis haggarti wasn’t a victim: it was a competitor. Measuring between 7 and 19 meters in length, with powerful jaws, long, flexible arms—the hunting strategy of octopuses doesn’t require a huge mouth, but rather limbs that can grasp and hold while the beak dismembers—and likely intelligence, these giant cephalopods probably occupied the same level in the food chain as mosasaurs. Whether they interbred, no one knows yet. But the possibility of an octopus the size of an articulated bus hunting marine reptiles is no longer science fiction. And, in any case, vertebrates and cephalopods arrived at the same point—becoming large, intelligent predators—by different, but surprisingly parallel, paths. Vertebrates lost their armor plates and reduced their scales to gain speed and agility. Cephalopods eventually shed their external shells to become soft-bodied animals that were faster, had better vision, and greater cognitive abilities. Both groups developed powerful jaws.
Ikegami admits that intelligence cannot be measured in a fossil, but it can be inferred: “Asymmetric wear does not directly prove intelligence, but it suggests that Nanaimoteuthis was not just a large and powerful predator: it may also have had advanced behavior and even individual behaviors, similar in some ways to modern octopuses.”
An inevitable question is where they lived. Modern giant octopuses inhabit the abyssal depths. But Ikegami rules out that Nanaimoteuthis led that kind of lifestyle: “It wasn’t a coastal environment, but neither was it the kind of deep-sea environment where many giant octopuses live today. It was a relatively open ocean environment, with diverse marine life. Nanaimoteuthis was probably a large predator; it used its long arms, powerful jaws, large body, and enormous mobility to capture and devour prey such as ammonites, large bivalves, fish, and other cephalopods.”
An AI that digs into stone
A fundamental part of the study was methodological. A dozen of the 27 beaks analyzed were not found with a pick and hammer, but with what the authors call “digital fossil mining”: a combination of high-resolution tomography—which generates images of cross-sections of the rock at a microscopic scale—and an artificial intelligence model, trained to detect organic structures, that is, animal remains, in huge sets of images.
The technique, developed by the team itself, made it possible to find jaws that would have gone completely unnoticed with conventional methods, they say, and to visualize them as digital three-dimensional models without damaging the rock that contains them.
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