This Bone-Crunching Octopus Was Nearly the Size of a Semitruck and May Have Feasted on Giant Reptiles 100 Million Years Ago

The massive invertebrates may have been top predators, according to an analysis of their fossilized jaws. The work suggests that ancient oceans weren’t completely ruled by spine-bearing creatures, as previously thought

April 27, 2026

illustration of an octopus — Illustration of the giant ancient octopus Yohei Utsuki, Department of Earth and Planetary Sciences, Hokkaido University

The late Cretaceous marine food web may have had a terrifying kraken-like creature among its top ranks. A new analysis of ancient octopus jaws suggests that many of the animals were bone-crunching apex predators that could grow to nearly the length of a semitruck, researchers report in a study published April 23 in the journal Science.

“To see a beak this size is quite amazing, to be honest. It was a massive animal. I certainly wouldn’t have wanted to go swimming in the ancient oceans if these things were swimming around,” Thomas Clements, a paleobiologist at the University of Reading in England, who did not participate in the study, tells the Guardian’s Hannah Devlin.

Researchers have long suspected that huge spine-bearing vertebrates, like sharks and reptiles, ruled the ancient seas. Meanwhile, octopuses and their fellow invertebrates were thought to be further down the food chain.

Digital fossil-mining of an octopus jaw fossil

But little is known about the archaic eight-legged creatures, since their soft bodies are seldom preserved as fossils. So the team behind the new study turned to 15 previously described fossilized beaks—hard mouthparts like those on parrots—found in Japanese and Canadian sediments dated to the late Cretaceous, around 72 million to 100 million years ago. Thanks to an artificial intelligence-assisted software, they identified another 12 specimens in rocks of similar age from Japan.

“Using this approach, we were able to discover fossil jaws that would have been nearly impossible to find using conventional techniques, and to reconstruct them as detailed 3D digital fossils,” study co-author Yasuhiro Iba, a paleontologist at Hokkaido University in Japan, tells National Geographic’s Jack Tamisiea.

The beaks belonged to a group of finned octopuses called Cirrata, which had ear-like flaps on their heads and webbing between their arms. Analysis of the jaws’ shapes, sizes and wear patterns suggests that the creatures were fearsome predators that munched on tough prey with forceful bites, since some beaks were missing up to 10 percent of their total length.

What’s more, the largest identified species, Nanaimoteuthis haggarti, may have reached lengths up to 62 feet, the team estimates. That would make it the biggest invertebrate ever recorded. The massive octopuses may have feasted on some of the largest ocean reptiles at the time, like plesiosaurs and mosasaurs.

“With their tentacles and their suckers, they could perfectly hold on to such an animal, and there is no escape,” Christian Klug, a paleontologist at the University of Zurich in Switzerland who did not co-author the study but reviewed the research, tells BBC’s Helen Briggs.

Quick fact: What’s the largest living invertebrate?

Today, giant squids are thought to be the biggest creatures without a backbone; the largest one documented was nearly 43 feet long. Some scientists suspect that colossal squids could be even bigger, but the jury is still out since they’re so hard to find.

Interestingly, Iba and his colleagues also found asymmetrical wear marks on the fossils, indicating the animals favored one side of their jaws. In modern animals, researchers link this behavior with advanced brain processing, so the early octopuses may already have been demonstrating a complex, intelligence-associated behavior.

The study’s results call into question the previously hypothesized food web organization of Earth’s early oceans. “It challenges the common view of an ‘age of vertebrates’ in marine ecosystems,” Iba tells National Geographic.

The fossils also push back the oldest documented finned octopuses by about 15 million years, and they move the oldest record of any octopus to as early as about 100 million years ago, around 5 million years earlier than past evidence.

The discovery follows a study published this month that found that the former record-breaking 300-million-year-old fossil of a supposed octopus actually isn’t an octopus. Instead, it’s probably a relative of a nautilus.

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