Fossil Evidence Points to Giant Apex-Predator Octopuses in Cretaceous Seas

by Riko Seibo
Sapporo, Japan (SPX) ) May 01, 2026
New research from Hokkaido University has found that the earliest known octopuses were not small, cryptic animals hiding in reef crevices but enormous apex predators that dominated Cretaceous marine ecosystems alongside large vertebrates. The study, published in Science on 23 April 2026, pushes the fossil record of octopuses back by approximately five million years to around 100 million years ago, and extends the record of the finned Cirrata group by 15 million years.

Because octopuses are soft-bodied animals, they leave almost no fossil trace. The research team focused instead on fossilized jaws - the only hard structure octopuses possess - recovered from Late Cretaceous rock samples in Japan and Vancouver Island, dating between 100 and 72 million years ago. High-resolution grinding tomography combined with an AI model was used to analyze the size, shape, and wear patterns on these ancient jaws in detail.

The results were striking. The jaws indicated animals of up to approximately 20 metres total length, placing these early octopuses at the very summit of the Cretaceous food web. Wear analysis revealed extensive damage to the jaw tips - chipping, scratching, cracking, and polishing accounting for up to 10 percent of jaw tip volume - consistent with repeated, forceful contact with hard-shelled prey.

"Our findings suggest that the earliest octopuses were gigantic predators that occupied the top of the marine food chain in the Cretaceous," said lead researcher Yasuhiro Iba of Hokkaido University. "The most surprising finding perhaps was the extent of wear on the jaws. This indicates repeated, forceful interactions with their prey, revealing an unexpectedly aggressive feeding strategy."

The uneven distribution of jaw wear also suggested lateralization - a preference for using one side over the other - which the researchers interpret as evidence of complex, coordinated behavior in these ancient animals.

The broader significance of the findings lies in what they reveal about the evolutionary potential of invertebrates. "This study provides the first direct evidence that invertebrates could evolve into giant, intelligent apex predators in ecosystems that have been dominated by vertebrates for about 400 million years," Iba said. "Our findings show that powerful jaws and the loss of superficial skeletons were essential to becoming huge, intelligent marine predators."

Research Report:Earliest octopuses were giant top predators in Cretaceous oceans