The sharkclub octopus, Galeoctopus lateralis, a new genus and species of deep-water octopus from the western Pacific Ocean (Cephalopoda: Octopodidae)

French and Australian research expeditions over the past three decades, to the deeper waters of the tropical Pacific Ocean, have encountered a distinctive new octopus. Galeoctopus lateralis is described here from 200-400 in deep in the southern and western Pacific Ocean. This small octopus is recognized by a distinctive jaw-like ligula in mature males, superficially resembling the head and jaws of a shark (complete with teeth-like lugs). Other distinctive characters include a lateral mantle ridge, skin sculpture including stellate papillae, and swollen distal oviducts in females. This combination of characters warrants recognition as a distinct genus. Relationships with other octopodid genera are discussed. We propose that the unique form of the male reproductive organ has evolved as a mechanism for reduction of sperm competition. The mouth-like ligula pit may function to pierce, rupture, grip and/or remove the sperm bulbs of previous suitors from the distal oviducts of the female. This morphology is compared with parallel structures in other cephalopods.