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
Mammal the early [[Permian]]. Nonmammalian synapsids are sometimes called "mammal-like reptiles". [[Therapsid]]s, a group of synapsids, descended from [[pelycosaur]]s in the Middle Permian, about 265 million years ago, and became the dominant land vertebrates. They differ from basal [[Eupelycosauria|eupelycosaurs]] in several features of the skull and jaws, including: larger skulls and [[incisor]]s which are equal in size in therapsids, but not for eupelycosaurs. The therapsid lineage leading to mammals went through a series of stages, beginning with animals that were very similar to their pelycosaur ancestors and ending with [[probainognathia]]n [[cynodont]]s, some of which could easily be mistaken for mammals. Those