Giant octopuses as apex predators of prehistoric oceans

The Scandinavian legend of the Kraken, a gigantic sea monster equipped with deadly tentacles, may be closer to the truth than anyone suspected. Japanese scientists suggest that 100 million years ago the oceans were ruled by giant octopuses. According to the latest research, they may have been the largest underwater predators of the late Cretaceous period.

XXL-sized jaws

The problem with octopuses is that, as mollusks, they belong to invertebrates, and their remains decompose easily, leaving behind very few fossils. Jaws are the only elements that have a chance of being preserved in relatively good condition for thousands or millions of years.

As early as a decade ago, in Japan and on Canada’s Vancouver Island, paleontologists managed to find 15 giant pairs of jaws belonging to octopuses that lived during the Cretaceous period (145–66 million years ago). Recently, more fossils have been added to this impressive collection – 12 pairs of jaws found in sedimentary rocks dating back 72–100 million years. The authors of the study, published on April 23 this year in the journal Science, conducted a detailed analysis of the collected material using AI models and specialized 3D tomography methods. The results turned out to be quite surprising.

Octopuses as apex predators

Until now, it was believed that vertebrates stood at the top of the food chain during the Cretaceous period – tyrannosaurs and triceratops on land, and marine reptiles and sharks in the depths of the oceans. The results of the work by the Japanese team led by paleontologists from Hokkaido University suggest otherwise: among the largest ocean predators 100 million years ago were giant octopuses measuring from 7 to as much as 19 meters.

The limited number of fossils makes it difficult to precisely determine the ecological role of late Cretaceous octopuses, but according to the authors of the study it is highly likely that they hunted the largest marine reptiles, including plesiosaurs and snake-like mosasaurs. This is supported by the high degree of wear observed on the analyzed jaws, corresponding to the effects of biting prey with harder body structures.

Everything indicates that ancient octopuses were carnivores that readily crushed bones and shells in their mouths. Interestingly, wear patterns point to a preference for one side of the jaw. According to scientists, this suggests that prehistoric krakens were capable of complex behavior indicative of advanced intelligence.

Fascinating evolution of octopuses

Japanese researchers identified two new species of prehistoric cephalopods within the analyzed fossils: Nanaimoteuthis jeletzkyi and Nanaimoteuthis haggarti. The latter were most likely the largest invertebrates known to science. Their long, powerful tentacles were used to capture prey, which they then attacked with their enormous beak.

The discovery is highly significant from the perspective of marine life evolution. It appears that in ecosystems dominated by vertebrates for 400 million years, highly intelligent octopuses of gigantic size had the opportunity to evolve. The results of our study show that powerful jaws and the loss of superficial skeletal structures – features common to octopuses and marine vertebrates – were essential for achieving large size and high intelligence in marine predators, says Prof. Yasuhiro Iba from Hokkaido University.

Modern octopuses, although much smaller than their late Cretaceous ancestors, have the highest brain-to-body mass ratio among invertebrates. Additionally, two-thirds of their 500 million neurons are located in their arms. As a result, they are surprisingly intelligent creatures, with cognitive abilities comparable to those of a three-year-old child, capable of deliberately using tools and solving puzzles or escaping from a maze.

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Source:
Shin Ikegami et al., Earliest octopuses were giant top predators in Cretaceous oceans. Science 392, 406–410 (2026). DOI:10.1126/science.aea6285