Pinniped Pinniped Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals). There are 33 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their
Pinniped Nunavut, Canada. 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 had been a quadrupedal swimmer—retaining a form of aquatic locomotion that give rise to the major swimming types employed by modern pinnipeds. The researchers who found "Puijila" placed it in a clade with "Potamotherium" (traditionally considered a mustelid) and "Enaliarctos". Of the three, "Puijila" was the least specialized for aquatic life. The discovery of "Puijila" in a lake deposit suggests that pinniped evolution went through a freshwater transitional phase. "Enaliarctos",