Fossil Jaws Reveal Ancient Giant Octopuses Up to 19 Meters Long

Giant octopuses may have dominated ancient oceans 100 million years ago during the age of dinosaurs, according to new research.

Some of the earliest octopuses are thought to have been formidable predators, possessing strong arms for grasping prey and beak-like jaws capable of crushing shells and bones.

A new study of exceptionally well-preserved fossil jaws suggests these animals reached lengths of up to 19 meters, potentially making them the largest invertebrates ever documented.

For decades, paleontologists assumed that the largest ocean predators were vertebrates like fish and reptiles, with invertebrates such as octopuses and squid playing secondary roles.

New research by scientists at Hokkaido University in Japan challenges this long-held view of ancient octopuses.

Their analysis of fossil jaws indicates that giant octopuses glided through ancient oceans, equipped with the ability to chew through the hard shells and skeletons of large fish and marine reptiles.

The study estimates a body length of about 1.5 to 4.5 meters, which, when including the long arms, yields a total length of roughly 7 to 19 meters.

Even at the lower end of that range, the animal would be enormous by modern standards.

Another striking feature is uneven wear on the fossilized jaws from left to right, suggesting the animals may have favored one side when feeding.

In living animals, lateralization — favoring one side of the body — is associated with advanced brain function.

Modern octopuses are renowned for their intelligence, problem-solving abilities, and complex hunting strategies.

The Giant Pacific Octopus, the largest living species today, can have an arm span exceeding 5.5 meters.

Video footage shows these octopuses taking on sharks more than a meter long.

“With their tentacles and their suckers they could perfectly hold on to such an animal and there is no escape,” said Christian Klug, a paleontologist at the University of Zurich, who reviewed the research.

However, many questions remain. Scientists can only speculate about the exact shape of the animals, the size of their fins, or their swimming speed.

And no fossil has yet been found with preserved stomach contents that would provide direct evidence of their diet.

Dr. Nick Longrich, a paleontologist at the University of Bath, said his hunch is that they mainly preyed on ammonites.

However, like modern octopuses, they would have been opportunistic and voracious predators, likely not passing up other prey if given the chance.

“It’s going to take a while before we figure this thing out,” he said. “It’s a bit of a mystery.”

For now, the fossils offer a tantalizing glimpse of a giant of the deep that may have roamed ancient seas, armed with a crushing jaw, powerful arms, and a brain that may have helped it compete with other top predators.

The research is published in the journal Science.