New investigations spearheaded by paleontological experts at Hokkaido University reveal that colossal, soft-bodied cephalopods, measuring up to an astonishing 19 meters (62 feet) in length, not only contended with but potentially preyed upon the most formidable marine reptiles of the Cretaceous epoch.
An artist’s impression of an ancient giant octopus. Image credit: Yohei Utsuki, Hokkaido University.
For vast geological periods, marine food webs were presumed to be solely governed by large vertebrate apex predators, with invertebrates relegated to the role of lesser prey.
However, a distinct evolutionary path was pursued by octopuses, diverging significantly from their shelled invertebrate counterparts.
Rather than relying on external armor, these marine inhabitants developed supple physiques, affording them unparalleled agility, enhanced visual acuity, and superior cognitive abilities.
Some of these species achieved gargantuan proportions and occupied the uppermost echelons of the predatory hierarchy; however, their exact ecological positioning remained somewhat enigmatic due to a paucity of definitive fossil evidence.
“Our discoveries indicate that the earliest octopuses were immense predators that commanded the zenith of the marine food chain during the Cretaceous era,” stated Professor Yasuhiro Iba, a paleontologist affiliated with Hokkaido University.
“Based on remarkably well-preserved fossilized mandibles, we have ascertained that these creatures attained total lengths approaching 19 meters, potentially exceeding the dimensions of large marine reptiles contemporary to that period.”
“Perhaps the most striking revelation was the degree of attrition observed on the jaw structures.”
Such wear, incurred through the act of forcefully impaling or crushing hard-bodied prey, manifests as characteristic damage analogous to that observed in extant shell-crushing cephalopods. Furthermore, the dimensions of an octopus’s jaw can serve as a metric for estimating its overall body mass.
Within the framework of their investigation, Professor Iba and his research team identified unambiguous indicators of wear on fifteen substantial fossilized jaws belonging to ancient relatives of octopuses, previously unearthed from Cretaceous geological strata in Japan and on Vancouver Island.
Moreover, employing a digital paleontology methodology, they unearthed twelve additional jaws from finned octopuses within Cretaceous rock formations in Japan.
Through the meticulous examination of these newly acquired specimens, two primary species were delineated: Nanaimoteuthis jeletzkyi and Nanaimoteuthis haggarti.
These particular finned cephalopods, with Nanaimoteuthis haggarti standing out, reached extraordinary sizes, spanning from 7 to 19 meters (23-62 feet), thus rivaling the scale of contemporary colossal marine reptiles and potentially representing the largest invertebrates documented to date.
Furthermore, in the most sizable specimens, the jaws exhibited considerable wear, with originally sharp edges in their juvenile forms progressively becoming blunted and rounded as they matured.
The observed patterns of wear strongly suggest that these beings were active carnivores, habitually employing powerful bites to fracture and consume hard exoskeletons and bony structures.
They are thought to have utilized their elongated, dexterous appendages to ensnare prey, subsequently dismembering it with their formidable beaks—a behavioral trait often associated with elevated levels of Gnetic intelligence.
“This research presents the inaugural direct substantiation that invertebrates could evolve into colossal, highly intelligent apex predators within ecosystems that had been predominantly governed by vertebrates for approximately 400 million years,” Professor Iba remarked.
“Our findings underscore the critical role of robust jaw structures and the forfeiture of superficial skeletal elements, characteristics common to both octopuses and extant marine vertebrates, in the evolutionary trajectory towards becoming massive, intelligent marine predators.”
The published findings were made available online on April 23, 2026, within the esteemed scientific journal Science.
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Shin Ikegami et al. 2026. Earliest octopuses were giant top predators in Cretaceous oceans. Science 392 (6796): 406-410; doi: 10.1126/science.aea6285
