The Cretaceous ocean once hosted a 19-meter octopus predator

Space · Published 22 October 2026 Swipe more like this →

In short: For decades, we imagined the mosasaur as the undisputed king of the prehistoric seas. But new research into fossilized beaks suggests that an invertebrate—an octopus so large it rivaled the biggest marine reptiles—once stalked the depths, hunting fish and crustaceans with massive arms and a powerful beak.

The discovery of Nanaimoteuthis haggarti challenges our perception of 'giant' prehistoric life. While most modern octopuses are roughly the size of a human hand, this species reached lengths of up to 19 meters. This makes it comparable in scale to a bowling lane, placing it among the largest invertebrates ever to inhabit Earth during the Late Cretaceous period (approximately 101 to 66 million years ago). This massive creature would have navigated the ocean depths as a fearsome carnivore. It successfully hunted various sea creatures including crustaceans and fish. These findings reveal how much larger these ancient animals were compared to any known modern relatives.

Researchers identified this super-predator by analyzing hard parts, specifically fossilized beaks found in Canada and Japan. By comparing these jaws to modern cephalopods, scientists estimated its massive proportions. The study involved 15 previously known fossil jaws plus 12 newly identified specimens from Japanese rocks. Because the soft tissues of octopuses do not fossilize, these ratios provide the primary evidence for a body shape similar to contemporary species. The research team specifically examined rocks from Japan to find these remains. They used reasonable and recent examples of cephalopods to calculate the size estimates. These findings are based on a total of 27 analyzed fossil jaws.

Nanaimoteuthis lived in an era of marine giants, competing with the 18-meter-long Mosasaurus hoffmannii and the 10-meter-long Elasmosaurus. While other cephalopods like Enchoteuthis melenae reached about 12 meters—similar to today's colossal squid—Nanaimoteuthis stands out as a unique apex predator. Its existence highlights the 'true power of invertebrates,' proving that complex, multi-armed hunters could dominate ecosystems alongside the largest vertebrates in history. In addition to other giants, the ammonite Parapuzosia seppenradensis reached two meters in diameter during this time. The study confirms that Nanaimoteuthis is now officially ranked among these enormous prehistoric invertebrates.

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