species have nonretractile claws. Early procyonids may have been an offshoot of the canids that adapted to more omnivorous diets. Pinnipedia (seals, sea lions, and walruses clade) is a widely distributed and diverse group of semiaquatic marine mammals which is closely related to an extinct group of pinnipeds, Enaliarctos. While support for the monophyly of pinnipeds is strong, the relationship of pinnipeds to terrestrial mammals is still unclear. Some studies support the hypothesis that the bears are their closest relatives, while others support a closer relationship to the mustelids. Pinnipeds split from other caniforms 50 million years ago (Mya) during the Eocene. The clade is currently divided into three families: Family Phocidae (true or earless seals) consists of around 19 species of highly aquatic, barrel-shaped animals ranging from and in length (the ringed seal), to and (southern elephant seal). Phocids are found throughout the world's oceans. Family Otariidae (eared seals, sea lions, fur seals) is distributed throughout the world's oceans with the exception of the North Atlantic. The 15 species (divided into seven genera) of otariids are distinguished from phocids by visible external ears (pinnae), more dog-like faces, and the ability to turn their rear flippers forward. Family Odobenidae currently includes a single species, the walrus. A large (), distinctive pinniped with long whiskers and tusks, the walrus has a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere. It is primarily a benthic forager of bivalve mollusks and other marine invertebrates. Evolution Caniforms first appeared as tree-climbing, superficially marten-like carnivores in the Eocene around 42 Mya. Miacis cognitus was probably an early caniform. Like many other early carnivorans, it was well suited for tree climbing with needle-sharp claws, and had limbs and joints that resemble those of modern carnivorans. M. cognitus was probably a very agile forest dweller that preyed on smaller animals, such as small mammals, reptiles, and birds. Debate continues on the origin of pinnipeds. Recent molecular evidence suggests pinnipeds evolved from a bear-like ancestor about 23 Mya during the late Oligocene or early Miocene epochs, a transitional period between the warmer Paleogene and cooler Neogene periods. However, discovery of the fossil Puijila darwini in early Miocene deposits in Nunavut suggests a different scenario. Like a modern otter, Puijila had a long tail, short limbs, and webbed feet instead of flippers. However, its limbs and shoulders were more robust, and Puijila likely