‘Kraken-Like’ giant octopuses as large as semi-trucks ruled oceans 100 million years ago, study finds

A new study suggests that giant, “kraken-like” octopuses may have been among the most formidable predators in Earth’s oceans roughly 100 million years ago, challenging long-held assumptions about marine life during the age of dinosaurs.

Tales of sea monsters with massive tentacles capable of sinking ships have long been part of maritime folklore. While those legendary creatures were fictional, new research published in the journal Science indicates that animals approaching such mythic proportions may have existed during the Cretaceous period, when dinosaurs dominated the land.

For decades, scientists believed that sharks and large marine reptiles ruled ocean food chains during this period, which ended about 66 million years ago. “When you think of the Cretaceous, you immediately think of mosasaurs and plesiosaurs,” said Neil Landman of the American Museum of Natural History, who was not involved in the study.


However, the new findings suggest early octopuses, including one species that may have reached lengths of up to 19 meters, comparable to a semitrailer truck, could have been equally dominant. The research challenges what Landman described as a “vertebrate-centric” view of prehistoric oceans, showing that “gigantic octopuses” may also have served as apex predators.

Studying ancient cephalopods has long posed challenges because their soft bodies rarely fossilize. “The fossil record is very patchy,” said Christian Klug of the University of Zurich, who was also not involved in the research. In many cases, the only remains are chitinous beaks, which must be carefully extracted from rock or analyzed using relatively low-resolution CT scans.

To overcome these limitations, researchers have turned to a technique known as “digital fossil mining,” developed last year by Yasuhiro Iba and Shin Ikegami of Hokkaido University. The method involves grinding away extremely thin layers of fossil-bearing rock, photographing each layer in high resolution, and assembling the images into detailed 3D, full-color models. Landman described the approach as “astonishing,” noting it has already helped uncover numerous hidden beaks and pushed back the known origins of major squid groups by millions of years.

In the latest study, the researchers reexamined 15 large fossil jaws previously attributed to early octopus relatives and applied their technique to Late Cretaceous sediments from Hokkaido Island in northern Japan, uncovering an additional dozen jaws. One specimen, measuring more than 80 millimeters, exceeds the size of the beak of the modern giant squid, Architeuthis dux, which can grow up to 12 meters in length.

All of the fossils were identified as belonging to two extinct octopus species, Nanaimoteuthis jeletzkyi and Nanaimoteuthis haggarti. Based on jaw size, the researchers Iba and Ikegami estimate that “N. haggarti” may have ranged from 7 to 19 meters in length. At the upper end, it would rank as the largest invertebrate ever described, suggesting that enormous octopuses once played a far more significant role in ancient ocean ecosystems than previously understood.