Fossilized Jaws Show Massive Ancient Octopuses Reached Over 60 Feet in Length

New analyses of fossilized jaws have revealed that massive, kraken-like octopuses hunted alongside other marine predators 100 million years ago. These octopuses had eight arms and long bodies that extended more than 60 feet. Researchers studied the jaws of 15 ancient octopus fossils previously found in Japan and Canada's Vancouver Island.

They also identified 12 more jaws from Japan using a technique called digital fossil mining, which closely scans rocks in cross-sections to reveal fossils hiding inside. Late Cretaceous-era waters were ruled by sharp-toothed sharks, mosasaurs, and plesiosaurs. Octopus beaks are made of stiffened chitin.

Researchers compared the jaws to those of modern-day octopuses to estimate sizes, determining that the ancient octopuses ranged from 23 to 62 feet in length. The largest jaw was substantially bigger than that of any modern octopus. The predator is one of the largest invertebrates on record.

An artist's reconstruction of a finned octopus of the species Nanaimoteuthis haggarti that reached a length estimated at up to 18.6 meters (61.02 feet) and lived about 86 to 72 million years ago during the Cretaceous Period, released on April 23, 2026. The largest creatures' jaws had significant wear and tear including scratches, chips, and rounded edges.

The wear and tear suggests the animals repeatedly crushed hard prey such as shells and bones. The findings were published on Thursday in the journal Science. A paleontologist with the American Museum of Natural History in New York who was not involved with the new research commented on the potential for further discoveries.

A prehistoric fossil previously thought to belong to the world's oldest octopus was reclassified earlier this month. The reclassified fossilized remains were listed by Guinness World Records as the earliest known octopus. The reclassified remains belong to a relative of a nautilus, a cephalopod with both tentacles and a shell.