The ancient whale may have been an amphibian of sea and land, feeding on fish in the sea during the day and returning to land at night. Primitive whales lived on land by hunting other animals and fish. Later, due to the lure of a large number of fish, they gradually moved to the sea.

From the anatomical point of view, many characteristics of cetaceans show a high degree of adaptation to life in the ocean. However, anatomical evidence is not enough to answer many questions about the origin of cetaceans.

But from the biochemical and genetic point of view, cetaceans are closely related to ungulates, and the fossil record (about 5 million years ago) also supports that cetaceans evolved from ungulates.

the ancestor of cetaceans is probably a terrestrial ungulate, Mesonychidae, which is produced in North America, Europe and Asia.

Some members of middle-claw animals are as petite as domestic dogs and some are as tall as bears, but the evolution process of many animals is from small to large, so cetaceans may have evolved from small middle-claw animals.

According to speculation, these middle-clawed animals, which have few teeth and fish in shallow waters, gradually changed into amphibious life forms and then became various whales and dolphins in the long evolution process.

Extended information:

Whales are divided into two types, one is baleen whales and the other is toothed whales.

Whales belong to Chordata, Vertebrate, Mammalia and Euthera, including about 98 viviparous mammals living in the ocean and rivers. There are more than 3 species in China waters.

all kinds of whales live in the sea except a few that live in fresh water.

Cetaceans are completely aquatic mammals, which look very similar to fish in appearance. Generally, the body length is between 1 meter and 3 meters, with bare skin, little hair on the snout and thick fat under the skin.

These fats help to keep body temperature. When they live in water, these fats can reduce the specific gravity of their bodies, which is beneficial to swimming.

Cetaceans are completely aquatic mammals, and some mainly rely on echolocation to find food and avoid enemies. Generally, they feed on mollusks, fish and zooplankton, and some species can also prey on seals and seals.

every once in a while, you must take a breath. Generally, in winter, they swim from high latitude cold water area to low latitude hot water area to give birth, and in summer, they swim back from low latitude to high latitude cold water area to prey.

Baidu Encyclopedia-Cetacea