Did kraken-like octopuses rule Cretaceous seas? Massive jaw fossils offer clues

Artist’s impression of an extinct Nanaimoteuthis species, often called krakens, which could have rivalled large marine reptiles in terms of size. Credit: Masato Hattori/Science Photo Library In the age of the dinosaurs, while Tyrannosaurus rex terrorized the land, gargantuan octopuses might have been among the top predators in the sea. Scientists have identified extinct octopuses — sometimes named krakens after the mythological monsters — that might have grown to nearly 19 metres in length. The estimate is based on fossilized jaws, which the researchers say show patterns of wear that came from devouring animals that had hard shells and skeletons. Their study, published on 23 April in Science 1 , challenges the idea that giant marine reptiles such as mosasaurs and other vertebrates exclusively dominated marine ecosystems in the Cretaceous period 143 million to 66 million years ago. But other scientists say the largest size estimates of the octopuses — around the length of an articulated lorry — and any firm conclusion about their role in ecosystems should be taken with a pinch of salt. Deep-sea denizens ‘Krakens’ have been identified from chitinous jaw fossils from the late Cretaceous . But their size range, diet and role in ecosystems were unclear, says study co-author Yasuhiro Iba, a palaeontologist at Hokkaido University in Japan. To plug such gaps, Iba, together with Hokkaido palaeontologist Shin Ikegami and their colleagues, reanalysed 15 large fossil octopus jaws. …