all being typical walrus breeding grounds. The archaic English word for walrus—morse—is widely thought to have come from the Slavic languages, which in turn borrowed it from Finno-Ugric languages, and ultimately (according to Ante Aikio) from an unknown Pre-Finno-Ugric substrate language of Northern Europe. Compare () in Russian, in Finnish, in Northern Saami, and in French. Olaus Magnus, who depicted the walrus in the Carta Marina in 1539, first referred to the walrus as the , probably a Latinization of , and this was adopted by Linnaeus in his binomial nomenclature. The coincidental similarity between morse and the Latin word ('a bite') supposedly contributed to the walrus's reputation as a "terrible monster". The compound Odobenus comes from (Greek for 'teeth') and (Greek for 'walk'), based on observations of walruses using their tusks to pull themselves out of the water. The term in Latin means 'turning apart', referring to their tusks. Taxonomy and evolution The walrus is a mammal in the order Carnivora. It is the sole surviving member of the family Odobenidae, one of three lineages in the suborder Pinnipedia along with true seals (Phocidae) and eared seals (Otariidae). While there has been some debate as to whether all three lineages are monophyletic, i.e. descended from a single ancestor, or diphyletic, recent genetic evidence suggests all three descended from a caniform ancestor most closely related to modern bears. Recent multigene analysis indicates the odobenids and otariids diverged from the phocids about 20–26 million years ago, while the odobenids and the otariids separated 15–20 million years ago. Odobenidae was once a highly diverse and widespread family, including at least twenty species in the subfamilies Imagotariinae, Dusignathinae and Odobeninae. The key distinguishing feature was the development of a squirt/suction feeding mechanism; tusks are a later feature specific to Odobeninae, of which the modern walrus is the last remaining (relict) species. Two subspecies of walrus are widely recognized: the Atlantic walrus, O. r. rosmarus (Linnaeus, 1758) and the Pacific walrus, O. r. divergens (Illiger, 1815). Fixed genetic differences between the Atlantic and Pacific subspecies indicate very restricted gene flow, but relatively recent separation, estimated at 500,000 and 785,000 years ago. These dates coincide with the hypothesis derived from fossils that the walrus evolved from a tropical or subtropical ancestor that became isolated in the Atlantic Ocean and gradually adapted to colder conditions in the Arctic. The modern walrus is mostly known from Arctic