Giant Octopuses Lived with the Dinosaurs
Scientists have found fossil evidence that the ancestors of today's octopuses were huge predators that swam alongside dinosaurs around 100 million years ago. A team from Hokkaido University in Japan, writing in the journal Science, says fossil jaws preserved in Late Cretaceous rocks show that these ancient octopuses grew to almost 20 metres long. That makes them as big as the largest marine reptiles of their time. The fossils were found in rock samples from Japan and Vancouver Island, and they completely change what we know about when finned octopuses first appeared.
Until now, the earliest known finned octopuses were thought to have lived only about 15 million years ago. Octopuses have soft bodies, so they rarely become fossils— only their hard jawbones tend to last. To find these tiny remains, the Hokkaido team used a technique called grinding tomography together with an artificial intelligence model. The jaws belong to an extinct group of octopuses called Cirrata, which could crush prey with their powerful bite. Dr Nick Longrich of the University of Bath thinks the giants probably hunted ammonites, though he says many questions remain.
Perhaps the most surprising finding was the heavy wear on the fossil jaws. Up to 10% of the jaw tip showed chipping, scratching and cracking— much more damage than is seen in any modern octopus today. This suggests the ancient octopuses had an aggressive way of feeding, attacking their prey with great force. The researchers say the discovery changes long-held ideas that only vertebrates ruled the Cretaceous seas. It is, in their words, the first clear proof that invertebrates can also evolve into giant, intelligent top predators in the age of dinosaurs.