What are placental mammals?
placental mammals, also known as infraclass eutheria (from the Greek EU-well [-sinful] "and " beasts ") are currently dominant in the form of territorial life on Earth, before them, and Prelycosaurs before them. The sister group Eutheria is Metheria, which includes warning and their extinct relatives. Eutherian is usually defined as any animal closely associated with living placental mammals than living marsons. This definition includes many extinct mammals. Monotremes include only six species, while Marsupials include about 350. Placental mammals have over 5,000 species, including humans and many animals of symbolic, practical and economical meanings for us, including dogs, horses, cows, pigs, mice, mice, etc. Placentary mammals have been up to 5.5 million years.
Like other mammals, placental mammals are covered with hair, endothermic ("warmly distorted") and have other brain layers (bark). Their body temperatureIt is slightly higher than Marsupials and Monotrems. They are distinguished by these other groups of mammals by a number of characteristics, including their genitalia, the separation of genitals and rectum and their vivipara (young stay inside the body until it fully develops). Although these types of animals are traditionally associated with living births, many other organisms practice it, including certain plants, fish, scorpions, some sharks, some snakes and velvet worms. It is assumed that Vivipary has evolved separately on many different occasions.
Placental mammals, who are dominant earthly vertebrates, occupied a number of ecological niches, from small gadgets to herbivores of all sizes to powerful carnivores as wolves and bears. Many of the largest members of the Eutheria class, including giant rodents, mammoths, saber tigers and many others, have disappeared over the last million years. The largest extinction wave appeared about50,000 years ago, when our ancestors spread across the planet and moved many species to extinction after their wake.
Placentary mammals have one of the most developed brains in the animal kingdom, culminating in order Carnivora (cats, dogs and relatives) and primates (gorillas, monkeys, people, etc.) Of course, all placental mammals were the most successful people. It is estimated that now numbers of about 7 billion individuals around the world, people, their pets and livestock are 99% of all earthly vertebrate biomass.