What's the difference between sea lions, seals, walruses and manatees?

Seals, seals, sea lions and walruses belong to the suborder Pinpoda of Carnivora of Mammalia, or are listed separately as Pinpoda.

Carnivora is the fourth largest order of mammals and one of the most important, diverse and familiar families. Some members of carnivores are at the top of the food chain and their importance is irreplaceable. However, due to human activities, almost all the top carnivores are on the verge of extinction, and many small carnivores are also threatened to some extent. Carnivora members are not all carnivores, but also omnivorous and even herbivorous members. They adapt to different living environments from sea to land and are almost distributed all over the world. The most important feature of Carnivora is that it has cracked teeth (fleshy teeth), which are composed of the last maxillary premolar and the first mandibular molar. Carnivora appeared as early as Paleocene, with abundant fossils, including some prehistoric creatures that people are most familiar with. All members of Carnivora are highly developed in intelligence, sensitive in smell, hearing or vision, and have stereoscopic vision. Compared with other early carnivorous groups, their rise may be the main reason for the extinction of those early types. Carnivores develop in two directions: canine and feline. The main difference between them is the structure near the skull base, especially the ear area. One of the dogs entered the ocean and became a mammal adapted to marine life. Carnivora, usually mainly terrestrial, is classified as Schipoda, Pinpoda and Pinpoda, which is a marine organism. Crown suborder/Archaeoptera is in Crown suborder (Ceratoptera) or Crown suborder (Ceratoptera), while Crown suborder is put into Jellyfish suborder/Archaea. Pinpoda is often upgraded to Pinpoda, which is juxtaposed with Carnivora, while dogs and cats can be upgraded to suborder. However, according to recent research, Pinpoda is not a single origin, seals and ferrets are more closely related, and sea lions and walruses are more closely related to bears, so Pinpoda is separated from these groups and grouped together. Recent research shows that dogs are far from other groups and may even be closer to cats. Dogs can be classified as Canoidea, other groups as Arctoidea, or dogs and cats can be put among cats and dogs, and others can be put among bears. The earliest carnivores were classified as extinct Microodonta or Microodonta superfamily, in which Miacoidea of Microodonta was closer to the ancestor type of Canine, Viverravidae of Civet was closer to the ancestor type of Cat, and some people classified the ancestor types of Canine and Cat in Microodonta into Canine and Cat respectively.

Pinpoda or Pinpoda is an aquatic carnivore. Its teeth are similar to those of terrestrial carnivores, but it is fin-like and spindle-like, which is very suitable for swimming. Pinnipeds usually live in water and feed in it, but they need to breed and rest on land. Pinnipeds usually gather on the shore in large groups during the breeding season, which is a male-female system, and males are several times larger than females. Pinnipeds have a thick layer of fat or fur to resist the cold of the sea. People often kill them in large quantities in order to get fat and fur, and their habit of gathering on the shore during the breeding season makes them easy to be killed, so many species are now in an endangered state, and some species may have become extinct. At present, there are three families of Pinpoda, which can be divided into two categories. Otariidae and Odobenidae, also known as ear seals, have small outer ear shells and large vital capacity, and most of the oxygen is stored in the lungs. Swimming is mainly propelled by forelimbs. When walking on land, their hind limbs fold forward and walk on all fours, which may have originated from bears. Dog fish family, also known as earless seals, has no outer ear, small lung capacity, and most oxygen is stored in the blood, which is suitable for deep diving. Swimming is mainly propelled by hind legs. When walking on land, the hind legs can't be folded forward, and they need to rely on body peristalsis to walk, which may be due to ferrets. Pinnipeds mainly feed on fish, crustaceans and mollusks, but leopard seals and some sea lions also prey on seabirds or other marine animals.

Eutetrigidae

The small sea lion family includes 5 species of sea lions and 8~9 species of sea dogs, which are similar in appearance. Sea lions are usually slightly larger, and the fur of sea dogs is of excellent quality, also known as fur sea lions or fur seals. Sea lions have slender bodies and long and powerful limbs. They are very flexible and quick in the water, chasing fish or other animals in the water, but they are not good at deep diving. Members of the sea lion family are also more flexible in walking on land, which is the most flexible on land among pteropods. Members of the sea lion family have a very high level of intelligence, and they are more flexible on land. Some species are often domesticated by aquariums for performances. Five species of sea lions belong to their genera, mainly distributed in the southern and northern parts of the Pacific Ocean. Southern species can enter the Indian Ocean and Atlantic Ocean around the southernmost tip of the mainland. Among them, Eumetopias jubatus, also known as the Shi's sea lion, is the largest sea lion, with a male weighing one ton, which is distributed in the Pacific Ocean and the northernmost sea lion. California sea lion Zalophus californianus, also known as sea donkey, is mainly distributed in California in the northeastern Pacific Ocean, and has also appeared in Japanese waters in the past. It is very small and often domesticated. Otaria byronia, a South American sea lion, is of medium size and distributed in the southern waters of South America. Australian sea lion Neophoca cinerea, also known as grey sea lion, is grayish white behind its head and distributed in the southern waters of Australia. New Zealand sea lion (Phocarctos hookeri), also known as Hu's sea lion, is distributed in Auckland Islands in southern New Zealand. Seals are divided into two genera: North and South. Beihai dog is just a kind of Callorhinus ursinus, also known as sea bear and cormorant. They are distributed along the coast of the North Pacific Ocean and have good fur quality. In China, they are called dragon skins, while the genitals of male animals are called seal kidneys or cormorants as traditional Chinese medicine. So seals are caught in large quantities and are in danger. There are many species of the genus Hemiptera in the South China Sea, which are widely distributed, ranging from the Galapagos Islands near the equator in the northernmost part to the Antarctic and sub-Antarctic areas in the southernmost part, and distributed in the southern coasts of South America, Africa and Oceania.

Odobey family of walruses.

The family Odobenidae includes only one walrus Odobenus rosmarus, a marine animal that lives exclusively in the Arctic Ocean and is named after its ivory-like canine teeth. Walruses are huge, with males weighing more than one ton. Although they can walk on land with flippers like sea lions, they are far less flexible than sea lions. Walrus's subcutaneous fat is particularly thick, which can resist the cold of polar seawater, and its skin presents different colors in water and land. Walruses mainly dig crustaceans and mollusks on the seabed with their tusks, and sometimes they eat fish, plants and even other marine animals.

Sealidae

Members of the seal family are obese, with thick neck and round head after subcutaneous fat, and the hind limbs and tail are connected together and always backward. They can only crawl on land with the help of their bodies, which is very clumsy, but they are quite flexible underwater, and they are good at deep diving, and can dive to the depth of hundreds of meters. The members of the family Sealidae can be roughly divided into two categories: northern and southern, and can also be divided into the subfamily Pseudoseal and the subfamily Monoseal. The distribution of seal subfamily is basically limited to the northern hemisphere, while seal subfamily can also be seen in the southern part of the northern hemisphere. Northern seals are usually smaller, no more than 2 meters long, mainly concentrated in the Arctic Ocean, and can also be seen in various waters in the northern temperate zone. Among the northern seals, people are most familiar with the spotted seal (Phoca vitulina) and the spotted seal Phoca largha (upper right), which are distributed in the Yellow Sea and Bohai Sea in China. Among the northern seals, Lake Baikal seal Phoca (Pusa) sibirica is the only freshwater seal distributed in Lake Baikal, which is still unknown. Another kind of seal distributed in lakes is the Caspian Sea seal (PUSA), which is distributed in the Caspian Sea, the largest saltwater lake in the world. It may have come here before the Caspian Sea turned into a lake. Southern seals are usually larger. The largest southern elephant seal, Mirounga angustirostris (upper left), weighs about 3 tons, and is the largest member of pteropods and carnivores. The southern elephant seal is distributed in the Antarctic and sub-Antarctic, and Mirounga leonina, another northern elephant seal, is distributed on the west coast of North America, far away from the southern elephant seal, but they are very similar. Elephant seals are not only huge, but also have retractable noses, which are quite similar to elephants. Elephant seals are sometimes called walruses, which are easily confused with walruses of the genus Walrus. Among the southern seals distributed in the northern hemisphere, there are several kinds of monk seals Monachus, including the Mediterranean monk seal Monachus monachus (lower left), the Hawaiian monk seal Monachus schauinslandi and the Caribbean monk seal Monachus tropicalis. They adapt to the warm ocean and are now very rare, among which the Caribbean monk seal has become extinct. The most special seal in southern China is the leopard seal Hydrurga leptonyx (lower right) from the south temperate zone to the South Pole. Leopard seals are the only seals that feed on warm-blooded animals. It has a big mouth, swims fast and preys on all kinds of seabirds and other marine animals. Unlike other seals, leopard seals mainly paddle with their forelimbs, not their hind limbs. Megalodon is a crab-eating seal and a close relative of leopard seal. They are similar in size and distribution range, but far from each other in habits. Crab-eating seals do not eat crabs, but feed on krill, which appears in large numbers in the southern waters. Krill provides abundant food for animals in the southern waters, and crab-eating seals are also one of the largest seals.