Fossilized jaws from ancient octopuses found in Japan and Canada's Vancouver Island reveal that massive, kraken-like creatures once patrolled the seas alongside dinosaurs roughly 100 million years ago, growing to lengths of more than 60 feet. The finding, published in the journal Science, pushes the giant octopus much closer to the front rank of Cretaceous marine predators.
Researchers studied the jaws of 15 ancient octopus fossils that had previously been recovered from those two locations. They then identified 12 more jaws from Japan using a technique they developed called digital fossil mining, which scans rocks in detailed cross-sections to reveal fossils hidden inside. By comparing the ancient jaws to those of modern octopuses, the team estimated that the creatures ranged from 23 to 62 feet in length.
Co-author and paleontologist Yasuhiro Iba of Hokkaido University said in an email that the largest jaw was substantially bigger than that of any modern octopus. The largest specimens' jaws also showed heavy wear, including scratches, chips, and rounded edges, suggesting that the animals repeatedly crushed hard prey such as shells and bones.
The discovery adds a new and largely overlooked animal to the roster of late Cretaceous ocean predators. Most accounts of those seas focus on sharp-toothed sharks and marine reptiles such as mosasaurs and plesiosaurs. Soft-bodied invertebrates like octopuses have long been assumed to be too fragile to compete at the top of the food chain, but their beaks, made of stiffened chitin, are tough enough to crush shelled and bony prey.
Part of the reason giant ancient octopuses have been so difficult to study is that their soft bodies rarely preserve well in the fossil record. Scientists have studied some giant octopus relatives from the dinosaur era and examined small octopuses that drilled into clams, but estimating overall body size has remained difficult without more complete remains.
University of Alabama paleontologist Adiel Klompmaker, who had no role in the new research, said in an email that "these krakens must have been a fearsome sight to behold." He was commenting on the scale and predatory potential suggested by the jaw measurements.
Without access to stomach contents, the team cannot say with certainty what the animals were eating or whether they directly competed with mosasaurs and other large predators. They could have fed on fish or snails, grabbing prey with flexible arms and crushing it with their beaks. Paleontologist Neil Landman of the American Museum of Natural History in New York, who was not involved in the research, said that searching for octopus fossils in other locations could help scientists better understand how these creatures fit into ancient 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."
