What Are the Differences Between Seals and Sea Lions?
Despite the similarities of outward appearance, true seals and sea lions have some noticeable differences, due to convergent evolution. The Phocidae, or family group to which the true seals belong, are believed to have descended from a terrestrial weasel-like ancestor, while the Otariidae, or sea lion family group, are thought to have descended from a terrestrial bear-like ancestor. True seals are termed "earless" because they lack an external ear flap, whereas in "eared" seals or sea lions an external ear flap is visible. There are other, somewhat subtle, differences between the front flippers of the two groups, but the hind flipper differences are noticeable. In seals, the hind flippers extend directly behind the body, and are not capable of rotation unlike the hind flippers of sea lions that are longer and may be rotated toward the front of the body. This causes differences between the two in locomotion when on land: seals move forward by caterpillar-like hitching movements; sea lions use their hind legs to walk or even gallop across land. Fur seals, actually in the sea lion group, having extremely long hind flippers. Fur seals are occasionally seen off the RNSP coastline farther out to sea, however, they do not come ashore here, and breed in the far northern Pacific.