Pontolis
Pontolis is an extinct genus of large walrus.  It contained three species, P. magnus, P. barroni, and P. kohnoi.
Like all pinnipeds, Pontolis was a heavily built amphibious carnivore. Pontolis lived along the Pacific coast of North America along what is now the western coasts of California and Oregon between 11.608 and 5.332 million years ago, during the Miocene and Pliocene.

Description 

The skull of Pontolis is  long, surpassing skulls of any other prehistoric pinnipeds and twice as big as the skulls of modern male walruses. This giant species was much larger than modern walrus, though like many other extinct walrus species, its upper canines did not develop into long tusks like those of the modern walrus. Pontolis reached more than  in body length, rivaling the extant southern elephant seal as the largest pinniped and member of the order Carnivora of all time. Weight estimates for Pontolis range between .

References

Miocene pinnipeds
Mammals described in 1905
Fossil taxa described in 1905
Prehistoric pinnipeds of North America
Odobenids
Prehistoric carnivoran genera