Giant 19-meter-long octopuses resembling the mythical kraken may have rivaled the apex predators of the Late Cretaceous oceans, according to new paleontological research involving ground-breaking digital fossil mining techniques.
Like the tentacled beasts of Scandinavian myth, these octopuses likely competed with other Cretaceous apex predators, such as mosasaurs. While large vertebrates are typically predators and smaller invertebrates are prey, the evolutionary path of these kraken-like cephalopods appears to have inverted that dynamic, according to a new paper published in Science. In the study, Japanese researchers used advances in digital fossil mining to uncover evidence of these ancient giants.
Evolving the Kraken
Many invertebrates evolved protective shells, reinforcing their role as prey. Octopuses, however, followed a different trajectory. Freed from the constraints of heavy external shells, they developed advanced intelligence, keen vision, and exceptional mobility—traits that enabled them to become active predators.
“Cephalopods evolved in a very different direction from most invertebrates, largely because they reduced or lost their external shells,” lead author Iba Yasuhiro of Hokkaido University told The Debrief. “This allowed them to develop flexible, highly mobile bodies. As a result, they were able to evolve high swimming ability, complex behavior, large body size, and advanced sensory systems.”
Despite their immense size, these ancient, kraken-like animals are largely absent from the fossil record, making their reconstruction difficult for paleontologists—a challenge that has required new digital approaches.
“The main reason is preservation. Many modern-type cephalopods, especially octopuses and squids, have soft bodies and lack large hard external shells,” Yasuhiro said. “Unlike organisms such as ammonites or many mollusks, most of their body decomposes after death. As a result, only a few hard parts—mainly the jaws—have a good chance of being preserved as fossils.”
“In addition, even those jaws are often hidden inside rocks, which makes them difficult to detect using conventional methods,” Yasuhiro added.
Reconstructing the Kraken
Using surviving jaw structures from the Late Cretaceous, dating to 100.5-66 million years ago, the Hokkaido University team reconstructed key features of these massive cephalopods.
“We estimate body size using allometric relationships observed in living cephalopods,” Yasuhiro explained. “In modern long-bodied finned octopuses, there is a well-defined relationship between jaw size and mantle length. In this study, we used a dataset covering all families of modern finned octopuses and about one-third of their known species.”
The team first used jaw size to estimate mantle length, then extrapolated total body length based on relationships observed in modern species.
“There is a range in the estimates, but this reflects differences among the modern species used for comparison, not random error,” Yasuhiro said. “While the exact size is uncertain, the conclusion that these animals were extremely large is robust.”
The Power of Ancient Kraken
Given how long ago these kraken-like creatures roamed the planet’s oceans, the researchers could not directly measure bite force, but they still made some important observations.
“The jaws show very strong wear, including chips, scratches, polished surfaces, and rounded edges. In the largest specimens, about 10% of the total jaw length appears to have been lost due to wear,” Yasuhiro said. “This is more intense than what is typically seen in modern cephalopods that feed on hard prey. It indicates that these animals were capable of repeatedly crushing hard structures such as shells and possibly bones.”
With a lack of stomach contents or identifiable bite marks on vertebrate remains, the precise diet of these kraken-like creatures remains somewhat of a mystery.
“What we can say is that Nanaimoteuthis haggarti reached a body size comparable to major vertebrate predators of its time, and its jaws show clear evidence of processing hard prey,” Yasuhiro said. “This suggests that these animals belonged to the same top predator tier and may have competed with large vertebrate predators within the same ecosystem.”
The researchers believe these animals likely captured prey with powerful tentacles before breaking it apart with their beaks.
Digital Fossil Mining
As Yasuhiro noted, one of the greatest challenges in studying these animals is that their fossilized jaws are often hidden within rock. The team addressed this using digital fossil mining, an emerging method he describes as a critical new direction for paleontology.
“The key point is not simply that fossils are hidden inside rocks. Paleontologists have always known that,” Yasuhiro explained. “The problem is that conventional approaches—physically breaking rocks, chemically dissolving them, or using X-ray CT—often cannot recover tiny, delicate, low-contrast fossils or their fine surface structures. In many cases, the fossils remain effectively invisible, or the crucial information is lost.”
The team generated high-resolution, full-color image datasets of rock interiors, which AI systems then converted into detailed 3D fossil models. According to Yasuhiro, this approach increases the likelihood of discovery by more than 10,000 times compared to traditional methods.
“What I would most like to find next are fossils or structures that completely change our view of past ecosystems—not only more specimens of known groups, but organisms and biological evidence that have been essentially inaccessible until now,” Yasuhiro said.
“For me, Digital Fossil Mining opens a new frontier in paleontology,” he added, “not just studying fossils we can already see, but systematically discovering the hidden fossil record that previous methods could not reach.”
The paper, “Earliest Octopuses Were Giant Top Predators in Cretaceous Oceans,” appeared in Science on April 23, 2026
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.