The oldest octopus possibly reached 19 meters in length — Reigned as a fierce apex predator with advanced intelligence

A research group including Associate Professor Yasuhiro Iba, Academic Researcher Shin Ikegami, and Graduate Student Kanta Sugiura from the Graduate School of Science at Hokkaido University in collaboration with Ruhr University Bochum (Germany), the Japan Synchrotron Radiation Research Institute, Morgenrot Inc., Osaka Metropolitan University, Niigata University, and Chuo University, has shown the possibility that octopuses from approximately 100 million to 72 million years ago (the Late Cretaceous period) reached maximum lengths of 19 meters and were apex predators possessing advanced intelligence.

The researchers achieved detailed observation and analysis by excavating fossils as digital data and reconstructing them in high definition using AI. The flexible body of the octopus, which lacks the features commonly seen in vertebrates such as bones or body-covering shells, may have driven its evolution into a marine apex predator. The results were published in the April 23 issue of Science.

For the past 400 million years, apex predators have traditionally been thought to consist exclusively of vertebrates with massive bodies and high athletic capabilities. In contrast, invertebrates have been presumed to be the prey of these predators, specializing in defense through structures like shells.

On the other hand, among invertebrates, cephalopods (including octopuses and squids) are thought to have exceptionally improved their athletic performance by substantially reducing their shells, leading to the evolution of their arms and eyes, and the acquisition of advanced intelligence.

Evolutionary studies based on fossils have shown that cephalopods exceeding 2 meters in length existed during the Mesozoic Era (approximately 251 million to 66 million years ago), the age of the dinosaurs. However, because their diets and ecological roles could not be determined from the fossils, their exact nature had remained unknown.

To address this, the research group combined a previously developed "digital fossil mining method" with an AI developed by Morgenrot Inc. and partners that is capable of processing massive datasets, allowing them to excavate fossils from inside rocks as high-resolution digital data. The digital fossil mining method involves grinding rocks at micrometer intervals and automatically repeating surface photography, thereby converting the entire rock containing the fossil into massive, terabyte-scale data. By utilizing this technology, the team newly discovered 12 octopus jaw fossils, including those of juveniles.

Adding these to 15 octopus jaw fossils previously discovered and reported in Hokkaido and Vancouver, Canada, they classified the octopus species of the Late Cretaceous period (approximately 100 million to 72 million years ago), estimated their body sizes, and compared the growth rates of each species. Furthermore, they inferred predation styles based on wear marks on the jaws.

The results revealed that 5 species, including those previously classified as non-octopuses, were consolidated into 2 species of the suborder Cirrina. The new specimens included the oldest record of octopuses, dating back approximately 5 million years earlier than previous records. Among the newly discovered octopuses, there were older and newer species. Based on data on the modern species, the estimated maximum total lengths of the older species are approximately 3 to 8 meters, and those of the newer species are 7 to 19 meters. This body size is possibly greater than that of contemporary marine apex predators, such as the Mosasaur (which reached a maximum of 17 meters).

By estimating the growth rate of each species from the progression patterns of jaw pigmentation, the researchers found that the newer species grew faster and reached a larger maximum size, demonstrating that cephalopods underwent rapid gigantism. The jaw wear marks for both species were significantly larger than those of modern octopuses, covering nearly 10% of the entire jaw, which suggests an extremely powerful biting force. Furthermore, the degree of wear differed between the left and right sides of the jaw, indicating the possibility of "handedness" (lateralization), which implies an advanced brain and high intelligence.

In conventional excavations, detailed scratches and fine details are often lost during the process of extracting only the fossil, but the research group's method allows for the collection of highly detailed information.

Iba stated: "We expect that the digital fossil mining method will shift the entire research process of paleontology into cyberspace, allowing us to visualize long-term evolutionary processes and the ecology of primeval organisms that were previously invisible."

Journal Information
Publication: Science
Title: Earliest octopuses were giant top predators in Cretaceous oceans
DOI: 10.1126/science.aea6285