“I certainly wouldn’t have wanted to go swimming in the ancient oceans if these things were swimming around.” The man saying it, palaeobiologist Dr Thomas Clements of the University of Reading, was looking at a beak.
The beak in question belonged to Nanaimoteuthis haggarti, an octopus relative from the Cretaceous. Compared against the modern giant squid, which reaches about 12 metres and had been regarded as the largest known invertebrate, its beak was bigger. Using the link between jaw size and body length in living finned octopuses, a team estimated the animal at between 7 and 19 metres in total length. That could make it the largest invertebrate on record.
The research, published in the journal Science, was led by Dr Yasuhiro Iba, a palaeontologist at Hokkaido University. Clements was not involved in it.
Beaks in the rock
Soft-bodied octopuses almost never fossilize, so little was known about their ancient relatives. The beak is the only rigid part of the body, and the study leaned on it.
The team re-examined 15 large fossil beaks that earlier work had assigned to vampire squids. The new analysis concluded they belonged to Nanaimoteuthis, a group of ancient octopus relatives. Digital imaging then turned up a further 12 octopus beaks hidden inside Cretaceous rock, dating to between 72m and 100m years ago.
Crunching bone
In the largest individuals the beaks were chipped, scratched and rounded off. Sharp features visible in small juveniles had blunted over time. Modern octopuses do not swallow prey whole; they seize it with long, flexible arms and take it apart with the beak, and the fossils point to the same method.
“It probably used its long arms to seize prey and its powerful lower jaw to crush hard structures such as shells or bones,” Iba said. Bony fish and shelled animals were on the menu. Giant marine reptiles such as mosasaurs, comparable in size, possibly were too.
“Our study shows that these were not simply large versions of modern octopuses,” Iba said. “They were giant predators at the very top of the Cretaceous marine food web. This changes the view that Cretaceous seas were dominated only by large vertebrate predators.”
A preferred side
One more detail: the beaks were worn more on one side than the other. That is evidence of lateralised behaviour, and the researchers suggest the animals may have had arm preferences for particular tasks, as living octopuses do, using some arms to explore and others to feed. “This indicates that these animals were not only powerful, but also behaviourally sophisticated predators,” Iba said.
Clements, the outside voice, welcomed that. “Whenever you see artistic reconstructions, it’s always a vertebrate eating a cephalopod,” he said. “It is quite nice to imagine an octopus eating a large vertebrate for once.”
Sources
Sources
- Did kraken-like octopuses rule Cretaceous seas? Massive jaw …
- 'Kraken-like' giant octopuses 100m years ago crunched bones of prey
