Finned octopus species alive today are all small, deep-sea animals that mostly live in pitch-black darkness thousands of meters beneath the surface of the sea. But a new discovery by a team of researchers in Japan, published in April 2026, found that the ancient octopus relatives were likely gigantic predators that roamed the late Cretaceous seas between 100 million to 72 million years ago. Huge fossil jaws have been uncovered in Cretaceous deposits near Japan and on Vancouver Island in Canada. Though they were known to be part of the cephalopods class that includes squid, cuttlefish and octopus, not much else was known about them for years.  “It was still unclear whether they were truly octopuses, how large they were, what they ate, and what role they played in the marine ecosystem,” study co-author Yasuhiro Iba, a paleontologist at Hokkaido University in Japan, told Mongabay by email. “[We] showed that they were Cretaceous octopuses … very large and probably powerful predators that processed hard prey.” The largest species found among the fossils belonged to the now-extinct Nanaimoteuthis haggarti. Estimates from its jaw size suggest that the octopus may have reached 6.6 to 18.6 meters (22 to 61 feet) in length. On the higher end, that’s around two-thirds the size of an adult blue whale, the largest animal to ever exist.  “That is an enormous size for an octopus,” Iba wrote. “It suggests that it may have been among the largest invertebrates ever known.” The scientists also found evidence of wear,…This article was originally published on Mongabay

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