pinnipedia

Pinnipedia is a clade of semi-aquatic marine mammals within the order Carnivora, comprising the seals, sea lions, and walruses. Members are adapted to life in both marine and terrestrial environments and occur in cold, temperate, and some subtropical seas.

The three living families are Odobenidae (the walrus), Otariidae (the eared seals, including fur seals and sea lions), and Phocidae (the true seals). Otariids have external ear flaps and can pivot or rotate their hind flippers to walk on land, while phocids lack external ears and move on land primarily with their forelimbs. Walruses are large, tusked pinnipeds.

Pinnipeds are thought to have evolved from a terrestrial carnivore ancestor during the Miocene, with the first pinnipediforms appearing around 25–30 million years ago and the modern families diverging later in the Miocene or Pliocene. In contemporary classifications, Pinnipedia is treated as a monophyletic group within Caniformia, though some taxonomic schemes differ in ranking.

In the sea, pinnipeds hunt fish, cephalopods, and crustaceans, using their flippers to swim with powerful, agile strokes. They breed on land or ice, and females nurse their pups for weeks to months, depending on species. Males often display sexual dimorphism and may guard or contest territories during the breeding season.

Conservation status varies by species. Pinnipeds face threats from climate change, habitat loss, pollution, bycatch, and hunting. Several species are protected by international treaties and national laws, and ongoing research informs management and conservation efforts.