A Science paper published Thursday adds octopuses to a prehistoric predator lineup long centered on sharp-toothed sharks and large sea reptiles such as mosasaurs and plesiosaurs. The work, based on fossilized jaws, reports that a kraken-like octopus form may have prowled dinosaur-era oceans roughly 100 million years ago and could have hunted alongside other marine predators.
University of Alabama paleontologist Adiel Klompmaker, who said he had no role in the new research, described the idea of the animals as striking. “These krakens must have been a fearsome sight to behold,” he said in an email.
The study examined fossilized jaws from 15 ancient octopus specimens previously found in Japan and Canada’s Vancouver Island. The researchers also identified 12 additional jaws from Japan using a technique they developed called “digital fossil mining,” which scans rocks in cross-sections to reveal fossils hidden inside.
By comparing the ancient jaws with those of modern-day octopuses, the researchers estimated that the extinct animals ranged from 23 to 62 feet (7 to 19 meters) long. They also found that the largest jaw was “substantially bigger than that of any modern octopus,” according to Hokkaido University paleontologist Yasuhiro Iba, a co-author of the study who spoke by email.
The paper further reports evidence of feeding behavior in the form of wear on the largest jaws, including scratches, chips and rounded edges. Iba said in an email that the jaw damage suggested the animals “repeatedly crushed hard prey such as shells and bones,” pointing to an octopus predator capable of handling tough material.
The researchers said the octopuses’ soft bodies make it difficult to know how large the animals grew in the first place because soft tissues do not preserve well. They argued that octopus beaks, made of stiffened chitin, are tough enough to crush shelled and bony animals, helping explain why octopuses might belong in the same predator tier as other large marine carnivores.
Still, the researchers acknowledged limits in what fossils can prove about ecology. Without access to stomach contents, they said it remains hard to determine exactly what the octopuses ate or whether they truly competed for prey with other top predators, noting that they could have eaten fish or snails by snatching prey with flexible arms and breaking it apart with their beaks.
Paleontologist Neil Landman of the American Museum of Natural History, who was not involved in the research, said finding more octopus fossils in additional locations could help clarify how octopuses fit into ancient marine food webs. “It’s a big old planet,” Landman said. “So we have lots to look at to piece together the marine ecosystem through time.”