A real-life Kraken stalked the seas of the late Cretaceous

TOKYO – The violent, predator-filled oceans of the late Cretaceous period, long thought to be dominated by giant marine reptiles and sharks, harbored another apex predator of staggering proportions. New research reveals evidence of colossal octopuses, estimated to be up to 60 feet long, challenging previous assumptions about the limits of invertebrate evolution and the structure of ancient marine food webs.

The discovery, published in the journal Science, details two new species of extinct octopus that rivaled the largest predators of their time. Using groundbreaking fossil reconstruction techniques, a team of international researchers has provided the first definitive proof of "Kraken-sized" cephalopods, rewriting a significant chapter in our planet's natural history.

"I wasn't expecting any octopus of this magnitude at all," commented Fernando Ángel Fernández-Álvarez, a zoologist at the Spanish Institute of Oceanography who was not involved in the study. "And we now have the proof that they were living in the past."

The Challenge of a Soft-Bodied Fossil

Understanding the deep history of cephalopods like octopuses has been a persistent challenge for paleontologists. The very nature of these animals—composed almost entirely of soft tissue—makes fossilization exceedingly rare.

• The Fossilization Bias: The fossil record heavily favors organisms with hard parts like bones, shells, and teeth. Creatures without a skeleton, such as jellyfish and octopuses, decompose rapidly, leaving little to no trace behind.
• A Scant Record: "There are very few, very rare records about the octopus and their evolution," explains Jörg Mutterlose, a paleontologist at Germany's Ruhr University Bochum and a co-author of the study. This scarcity has created significant gaps in our knowledge of how these intelligent creatures evolved and what role they played in prehistoric ecosystems.

The only consistently hard part of an octopus is its beak-like jaw, which is made of chitin. It was the search for these elusive components that drove the new research.

A Breakthrough in Digital Fossil-Mining

The discovery hinged on a novel approach conceived over a decade ago by Yasuhiro Iba, a paleontologist at Hokkaido University and the study's lead author. He suspected that evidence of ancient octopuses might be preserved inside concretions—large, hard masses of rock that form on the seafloor around decaying organic matter.

"We thought there was a real possibility that octopus remains might also be hidden inside them," Iba stated, "even if nothing was visible from the outside."

To test this hypothesis, the team developed a meticulous technique they call "digital fossil-mining."

• The Process: Researchers collected concretions from 100-million-year-old deposits in northern Japan. They sliced the rocks into thousands of thin sections and digitally photographed the surface of each slice.
• AI-Powered Reconstruction: An AI model then assisted in identifying fossilized material within the images and digitally reassembling them into high-resolution 3D models.

This innovative, non-destructive process unveiled what lay hidden inside the rock: the perfectly preserved jaws of two colossal, previously unknown octopus species. "It is very similar to the beak of a bird," said Mutterlose, consisting of a shovel-like lower jaw and a sharp upper jaw used for chomping down on prey.

What the Jaws Reveal

The enormous beaks provide an unprecedented window into the biology and behavior of these ancient leviathans. Just as archaeologists can reconstruct an animal's life from its teeth, the research team used the jaws to extrapolate key details about these Cretaceous octopuses.

• Unprecedented Size: Based on the size of the lower jaws—the largest ever found for an octopus—the researchers calculated a total body length of up to 60 feet (approximately 18 meters). This would make them significantly larger than today's largest known species, the giant Pacific octopus, whose arm span rarely exceeds 13 feet, and establishes them as the largest invertebrates ever described.
• A Diet of Hard Prey: The 3D models revealed extensive chips, scratches, and wear patterns on the beaks. This physical evidence strongly suggests the octopuses fed on prey with hard exoskeletons, such as large crustaceans, bivalves, and ammonites. Mutterlose notes the octopuses would have used their powerful arms to "tear it apart into pieces" before consumption.
• Evidence of Advanced Brains: Crucially, the wear on the jaws was asymmetrical, with the right side showing significantly more erosion than the left. This "single-sided usage," Mutterlose suggests, indicates brain lateralization—the same functional division of brain hemispheres seen in humans and other advanced animals. This finding implies that the complex intelligence modern octopuses are famous for may have roots stretching back 100 million years.

"Modern octopuses are intelligent, flexible, and very unusual predators," said Iba. "Our results suggest that some of those remarkable traits may already have been emerging in early octopuses during the Cretaceous."

Implications for a Prehistoric World

This discovery fundamentally alters the scientific understanding of the late Cretaceous marine ecosystem. The existence of such a massive invertebrate predator introduces a new dynamic to a food web once thought to be exclusively ruled by vertebrates like the 50-foot mosasaur and giant sharks.

The findings confirm that octopuses were not just peripheral players but were capable of achieving apex predator status, competing for resources at the very top of the food chain. While speculative, the researchers suggest these giants may have even been capable of hunting other large animals.

Looking ahead, the success of the digital fossil-mining technique opens a new frontier for paleontology. Researchers can now revisit rock collections worldwide, applying this method to search for other soft-bodied organisms that have been missing from the fossil record. This study is not just the discovery of a single creature, but a proof-of-concept that could unlock countless other secrets of life's deep past, long thought to be lost to time.