In the scientific community, there are many debates concerning the ancestry of eared and true seals. Seals and sea lions have several visible differences.
Sea lions have external ear flaps and can move easily on land.
A flexible pelvic girdle enables them to rotate their hind flippers underneath to walk like other four-legged animals. Seals have a small opening for an ear and lack an external ear flap. To move on land, seals propel their streamlined body similar to a caterpillar. Both seals and sea lions are professionals in the water environment. Sea lions gain speed by porpoising, gliding on the water's surface to minimize resistance.