A research group comprising researchers from Hokkaido University, Ruhr University in Germany, the Japan Synchrotron Radiation Research Institute (JASRI), Morgenrot Inc., Osaka Metropolitan University, Niigata University, and Chuo University has used AI techniques to estimate the total length of an octopus jaw fossil from the Late Cretaceous period (approximately 1 to 7,200 million years ago), revealing that it could have reached a maximum length of 7 to 19 meters.
Until now, it was believed that for the past 4 million years in the oceans, giant vertebrates such as sharks and whales have monopolized the position of apex predators at the top of the food chain.
In contrast, invertebrates have evolved as small prey animals with shells and other defensive structures. However, cephalopods, including octopuses, are an exception; they lost their shells but improved their mobility, and some species grew to over 2 meters in length during the Mesozoic era (approximately 251 to 66 million years ago). Given that octopuses today thrive as highly intelligent, mid-level predators, it's possible they were predators in past ecosystems as well.
In this study, we used AI to visualize large-scale 3D data to analyze jaw fossils of Late Cretaceous octopuses and reconstructed their body size from jaw size based on measurements of closely related modern species. As a result, we estimated that the octopus could have been up to 19 meters long, suggesting that it may have surpassed even the extant giant squid (up to 12 meters), which has been considered the largest invertebrate in Earth's history, and vertebrates such as mosasaurs (up to 17 meters), which have been considered the apex predator of the Cretaceous period.
Furthermore, analysis of wear marks on the jaw fossil, visualized in high resolution using an AI model, revealed chips and scratches formed when crushing hard shells and bones, suggesting that Cretaceous octopuses were ferocious carnivores. In addition, the unevenness of wear on the left and right sides suggested the possibility that they possessed a "dominant hand," indicating a high level of intelligence.
Vertebrates acquired jaws approximately 4 million years ago, simultaneously losing hard tissues covering their body surface such as scales, while simultaneously enhancing their mobility and becoming apex predators. Octopuses, too, are thought to have evolved into some of the largest apex predators in the Cretaceous oceans by losing their shells and developing flexible bodies and strong jaws. This commonality suggests that the acquisition of jaws and the loss of hard tissues covering the body surface were key factors in the evolution of apex predators in the ocean.
This research represents a significant update to our understanding of marine ecosystems and their evolutionary history, which has long been considered primarily from the perspective of vertebrates.
Research paper information: [Science] Earliest octopuses were giant top predators in Cretaceous oceans
