Within Pinnipedia, seals are further classified into two families:
* Phocidae (True Seals): This family includes seals that lack external ear flaps and have small flippers that are not as flexible as those of eared seals. Examples include harbor seals, gray seals, and leopard seals.
* Otariidae (Eared Seals): This family includes seals that have prominent external ear flaps and larger flippers that can be rotated for use in walking on land. Examples include sea lions and fur seals.
So, to be more specific:
* Harbor seal, gray seal, leopard seal: Phocidae (True Seals)
* Sea lion, fur seal: Otariidae (Eared Seals)