Sea lions have outer auricles, while seals have no outer auricles, only ear holes. So seals and sea lions can be called earless seals and eared seals respectively. In the following two pictures, the difference between ears and ears is very obvious-

2. Land posture.

Seals can't move their hind limbs forward, so they can only wriggle, making it difficult to move on land; Sea lions (and walruses) can support their bodies forward with their hind legs, so they can walk or even run on land. The following picture shows the comparison of the bone structure of the hind limbs between sea lions and seals. (Image from Wikipedia)

3. Swimming posture.

Seals move forward by swinging their hind legs in the water, and their forelimbs move less, which seems to be basically crawling in the water; However, sea lions move forward by sliding their forelimbs in the water, and their hind limbs are basically motionless. It seems to be basically "flying" in the water.

Let's talk about others: walrus: tusks.

Seals: Seals are sea lions. At present, the sea lion family is divided into two subfamilies: sea lion subfamily and sea dog subfamily. The difference lies in the thickness of fur. The fur of sea dogs is thick and soft, so it is also called "fur sea lion". Some people think that this classification difference does not make much sense.

Manatee and dugong: Manatee's tail is round, and dugong's tail is V-shaped tail fin.

Taxonomically, among the three living families of Pinpoda, the sea lion family is closely related to the walrus family, while the seal family is a little far away. From the evolutionary source, it was generally believed that sea lions and walruses were closer to bears, while seals were closer to ferrets. However, a paper in nature in 2009 thought that the order Pinpoda had a single evolutionary origin, but the author didn't know which one was closer to bear or ferret.