It has been about 654.38 million+00,000 years since the appearance of Baki Kaitaos, and cetaceans have taken another step towards ocean evolution. The representative animal at this stage is the 4-meter-long "Anbiyurokethaus", which means an amphibious whale or a walking whale. If Bakiketaus is like a wolf, Anbiyurokethaus is like a crocodile. Anbi Yurokethaus discovered it earlier than Bakikethaus. Researchers believe that Anbiyurokethaus is a transitional animal in the development of cetaceans. The biggest ecological feature of Anbiyurokethaus is that it lives in the sea and on land, and mostly feeds on marine fish and drinks seawater. It is generally believed that all mammals form teeth and bones through oxygen atoms of water molecules in food. There are three kinds of oxygen isotopes in nature. When they have a specific ratio, the ratio between seawater and fresh water is different. Therefore, when analyzing the skeleton fossils of Anbi Yurokethaus, it shows that the isotope ratio of fresh water is more, which means that Anbi Yurokethaus ate animals on land, thus creating his own bones and postures.
Its ecology is somewhat close to that of crocodiles today. Eyes are very small. If the body is in the sea, the eyes are out of the water to observe the surrounding situation. The analysis of its skeleton shows that the hind toe is long and suitable for swimming in the water, while the front foot is not so long, which is conducive to climbing out. They often lurk in shallow water, observing all the way, waiting for an opportunity to sneak up on passing animals.
Locteau us
After "Anbiyurokehaus", an animal with the appearance and body shape of an otter, and the ancestors of whales such as "Lodketaus" which still maintain many characteristics of "Anbiyurokehaus" appeared one after another. And this animal, Lord Kettaus, is considered to have completely adapted to life in the water. It took about 3-4 million years from the appearance of Baki Ketaous to the appearance of Lord Ketaous. However, this is a brief moment in paleontology.
Dalton, Brazil and Lothar urs.
Then, about 39 million years ago, whales with streamlined bodies, such as Dalton and urs of Brazil, appeared, and they could swim smoothly in the ocean. They have lost their ancestors' long tails and replaced them with tail fins. Dalton, who is 4.5 meters long, has a skeleton similar to that of dolphins today, but there are some traces of hind feet degeneration. "Urus, Lothar, Brazil" has a slender body like an eel, with a total length of about 18 meter, which is larger than most existing whales in the world. But it also has two small hind feet.
Cetaceans who went to "urs, Losa, Brazil" after Baki Kaitaos are taxonomically called extinct protocetaceans. Among them, "Dalton", which has the characteristics of modern whales, later evolved into modern toothed whales and baleen whales. However, scientists believe that no animal skeleton fossils related to modern whales have been found in Dalton.
It is generally believed that the period when the original ocean developed to baleen whales and toothed whales, that is, about 34 million years ago, was a period of global sea level decline. At this time, there should be many places in the global stratum to be excavated. With luck, people should be able to find fossils of transitional species from primitive whales to modern whales.
In the history of biological evolution, there has always been a missing link from ancient land quadrupeds to today's aquatic mammals. Therefore, scholars believe that the ancient whale fossils found above just fill this gap. However, why did ancient whales migrate from land to water? It turns out that ancient whale breeding and rearing activities were all carried out on land, just like sea lions, seals, seals and other animals. However, the evolution of organisms is often influenced by environmental changes. About 50 million years ago, because the ratio of food to predators in the water was easier for ancient whales to survive than in the land environment, they began to enter the shallow sea near the shore. About/kloc-0.0 million years ago, the descendants of ancient whales evolved very similar to modern whales. They have a tail and a short neck, and their hind feet degenerate into fin-like appendages. They were used to living in the sea and never went ashore again.