Fossilized jaws from 80 million years ago reveal octopuses grew to 60 feet long, challenging the view that soft-bodied invertebrates couldn’t dominate ancient seas.
How researchers estimated the size of extinct octopuses
The team studied 15 known octopus jaw fossils from Japan and Vancouver Island, then used a new method called digital fossil mining to find 12 more jaws hidden in rock cross-sections. By comparing these ancient jaws to those of modern octopuses, they calculated body lengths ranging from 23 to 62 feet. The largest jaw belonged to a creature substantially bigger than any living octopus today.
Why the discovery changes perceptions of prehistoric predators
For decades, marine reptiles like mosasaurs and plesiosaurs were considered the top ocean predators during the Cretaceous period. Octopuses were overlooked because their soft bodies rarely fossilize, leading to assumptions they were too fragile to hunt large prey. But the wear patterns on these jaws — scratches, chips, and rounded edges — indicate repeated crushing of hard shells and bones, suggesting active predation on tough targets.
What this means for the record of largest invertebrates
Until now, the modern giant squid held the title at about 39 feet in length. The ancient octopus, potentially reaching 62 feet, surpasses that by nearly 60 percent. Paleontologist Yasuhiro Iba of Hokkaido University noted this makes it one of the largest invertebrates ever documented, though direct evidence of stomach contents is still missing to confirm its exact diet or competitive role.
How did scientists find fossils inside rocks without breaking them open?
They used a technique called digital fossil mining, which involves scanning rocks in cross-sections to reveal fossils hidden within the stone.
Why don’t we usually find octopus fossils from the dinosaur era?
Octopuses have soft bodies that lack hard parts, so they rarely fossilize; only their hard beaks and jaws tend to preserve under rare conditions.
