Newfound Fossil Octopus and Squid Were Giants

by Brian Switek

A good fossil squid is hard to find. The invertebrates are too squishy to leave much behind, and only in truly exceptional circumstances do paleontologists get to see much more than the chitinous supports the cephalopods kept on the inside. Octopus are even more confounding. Without any remnants of an internal shell, the eight-armed quick-change artists are like prehistoric ghosts. But do not despair. The jaws of ancient coleoids give us reason for hope, and have just revealed a pair of prehistoric cephalopods that may have rivaled today’s ocean giants in size.
Described by Kazushige Tanabe and colleagues in Acta Palaeontologica Polonica, the two lower jaws were found in roughly 80 million year old rock around Hokkaido, Japan’s Haboro-futamata Dam. Both were preserved in three-dimensional detail, providing Tanabe and coworkers with enough anatomical clues to figure out that they were left behind by previously-unknown species.
Octopus and squid beaks can be very informative fossils. That’s because marine biologists have spent a great deal of time studying the chitinous beaks of modern cephalopods. (Not much more than beaks and hooks are left in the guts of squid-eating whales, for example.) So by comparing the shape of the fossil lower jaws with those of fossil and modern cephalopods, Tanabe and coauthors were able to narrow down what sort of creatures the fossil beaks represent.
One of the jaws, assigned to the new species Nanaimoteuthis hikidai, most closely resembled those of today’s vampire squid. Don’t be thrown by the name. The lineage actually falls on the octopus branch of the cephalopod family tree. All the same, based on the relationship between beak size and body length in the modern species, Tanabe and colleagues estimated that their fossil octopus had a mantle length – or, the body minus the arms – of over two feet. That might not be It Came From Beneath the Sea proportions, and it’s assuming that the fossil species was similar to its only living relative, but it’s still pretty big for an octopus.

The lower jaw of Haboroteuthis poseidon. 

The other fossil beak sat in the mouth of an even larger cephalopod. Named Haboroteuthis poseidon by the researchers, the creature was a Cretaceous member of the lineage that contains modern squid. And from its jaw size, it was quite an impressive invertebrate.
Measuring a ridge that runs up the front of squid beaks, Tanabe and coworkers found that Haboroteuthis had a “crest length” of about 2.4 inches. A 25-foot-long giant squid caught off New Zealand, by contrast, had a crest length of only 1.8 inches, and a Humbolt squid with a mantle length of almost five feet had a crest length of 1.9 inches. Haboroteuthis was at least comparable to these modern heavyweights. We may never know for sure exactly how large Haboroteuthis was, but, if its jaw is anything to go by, it was as big as some of today’s undersea giants.