Large apex predators dominated the waters of the Late Cretaceous Period — think giant reptiles, such as plesiosaurs and mosasaurs, and kraken-like octopuses as long as a five-story building.
The latter included Nanaimoteuthis jeletzkyi and Nanaimoteuthis haggarti, some of which may have reached breath-taking lengths of almost 62 feet (19 meters) and feasted upon reptiles, including the plesiosaurs and mosasaurs.
A new paper, published in Science, not only extends the record for the earliest known octopus by 5 million years to the earliest Cenomanian (approximately 100 million years ago), but suggests some were ruthless hunters that sat at the very top of the food chain.
“This study provides the first direct evidence that invertebrates could evolve into giant, intelligent apex predators in ecosystems that have been dominated by vertebrates for about 400 million years,” Professor Yasuhiro Iba of Hokkaido University, Japan, said in a press release. “Our findings show that powerful jaws and the loss of superficial skeletons, common characteristics of octopuses and marine vertebrates, were essential to becoming huge, intelligent marine predators.”
Estimating the Kraken-Like Octopus Body Size
For this study, Iba and colleagues analyzed 27 octopus jaws from Japan and Vancouver Island, Canada. This included 12 fossils belonging to a group of finned octopuses, called Cirrata, discovered with digital fossil-mining techniques that involve high-resolution grinding tomography and artificial intelligence. By comparing jaw lengths to the proportions of modern-day finned octopuses, the team could estimate the octopus’s total body size.
The researchers identified two species — N. haggarti and N. jeletzkyi. The former is thought to have lived around 86 million years to 72 million years ago and would have reached lengths comparable to (and possibly exceeding) the giant marine reptiles of the time. According to the team’s estimates, individuals could grow to around 22 to 61 feet (6.6 to 18.6 meters) from mantle to tentacle.
N. jeletzkyi is an older and smaller species, existing 100 million years to 72 million years ago. With lengths ranging between 9 and 25 feet (2.8 to 7.7 meters), its size was roughly equivalent to two to five humans.
Read More: Octopus Arms Can Punch, Lift, and Sometimes Pull 100 Times the Sea Creature’s Own Weight
Determining the Ancient Octopus Diet
The jaws also offer clues to the ancient sea creatures’ food preferences. Even well-preserved jaws showed signs of wear, suggesting a diet consisting of large reptiles. The sheer amount of wear was one of the most surprising findings, said Iba.
“In well-grown specimens, up to 10 percent of the jaw tip relative to the total jaw length had been worn away, which is larger than that seen in modern cephalopods that feed on hard-shelled prey,” Iba explained in a press release. “This indicates repeated, forceful interactions with their prey, revealing an unexpectedly aggressive feeding strategy.”
Wear patterns also show a preference for using one side of the jaw over another. This, researchers say, suggests the octopuses were displaying complex behavior that signals advanced intelligence.
A Real-Life Kraken?
For centuries, sailors around the world have feared krakens and other mythical cephalopods, believed to be able to sink ships. This includes the Akkorokamui in Japan and the Te Wheke-a-Muturangi in Māori mythology.
It is thought that these legends were inspired by sightings of the giant squid, a species that can grow to impressive lengths of 33 feet (10 meters) or more. This new piece of research adds a new layer to the story — even if N. haggarti and N. jeletzkyi were long gone before humans took to the oceans.
Contrary to previous narratives, it appears marine invertebrates took on a larger, more predatory role during the Late Cretaceous, and these ancient cephalopods were already starting to show signs of intelligence.
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