Pinnipediformes

Pinnipediformes is a taxonomic grouping that includes the pinnipeds—the seals, sea lions, and walruses—and their extinct relatives. In many classifications it is treated as a clade within Caniformia, part of the order Carnivora. The term is used in some phylogenetic schemes and may be ranked as an infraorder, suborder, or unranked lineage; the more widely used term for living members is Pinnipedia.

Extant pinnipediformes are divided into three families: Phocidae (true seals), Otariidae (fur seals and sea lions), and Odobenidae (walruses). They share adaptations for aquatic life, including streamlined bodies, a thick insulating blubber layer, and limbs modified into flippers. Otariids retain external ears and can rotate their hind flippers to walk on land, while true seals lack external ears and move on land with a more awkward, belly-first gait. Walruses are large, tusked pinnipeds that feed mainly on benthic invertebrates and use their tusks in social and ecological contexts.

Pinnipediformes species are distributed worldwide in coastal and polar waters, occupying a range of habitats from rocky shores to sea ice. They are generally highly aquatic but depend on periodic haul-outs for breeding, molting, and rest. Reproduction is seasonal in many species; lactation periods and pup development vary by species. Diet typically includes fish, cephalopods, and crustaceans, with foraging strategies ranging from shallow benthic feeding to deep diving.

The fossil record shows pinnipedimorphs arising in the Oligocene to Miocene, with early semi-aquatic relatives giving rise to the three modern families. Many species face threats from habitat loss, climate change, and human activity, leading to ongoing conservation concerns.