All mammals (mammals, there are 20 orders of mammals in the world, a total of 4010 species), all turtles (about 257 species in 12 families), crocodiles (more than 20 species), all amphibians (frogs, salamanders, salamanders, a total of 5743 known species) are four-legged, adding up to tens of thousands.
I wonder if you’ve watched Animal World on TV before. This section has led us to know all kinds of animals in the world and their habits. Let us also learn more about the laws of nature, so who knows what the four-legged animals have? Today, Xiao Bian came to tell everyone.
Mammals refer to animals that breastfeed young children. They are the groups with the highest morphological structure and the most perfect physiological function in the animal world. The first mammals are 0.2 billion two thousand years ago, and there are more than 4,000 species in existence. Generally speaking, the intelligence level of mammals is higher than that of other species. All mammals have bones and fur. They breathe with lungs. Almost all mammals are viviparous. Common mammals include dogs, cats, pandas, elephants, monkeys, rabbits, tigers, etc.
Commonly known as turtle, refers to all members of the order Terrapin, is the oldest living reptile. The turtle has strong limbs and a very strong carapace. When attacked, the turtle can withdraw its head, tail and limbs into the shell. Turtles are sea turtles that can usually live on land and in water, and there are also sea turtles that live in the sea for a long time. Turtles are also long-lived animals, with a lifespan of more than a hundred years in the natural environment.
The crocodile is a cold-blooded oviparous animal, one of the earliest and most primitive animals found alive to date. It is a contemporaneous animal with the dinosaurs and is a carnivore, and there are 23 recognized species of crocodiles. Crocodiles are wild animals with high ecological, scientific and economic values. Therefore, some countries in the world actively develop crocodile farming.
Amphibians are four-legged vertebrates with bare skin and no scales (except for some lumbricoides) , covered with hair, etc. , but secrete mucus to keep the body moist; Its larvae live in water, breathing with their gills and breathing in their lungs and skin when they grow up. Common amphibians: rain frogs, tree frogs, toads, salamanders, mountain turtles, stone frogs and salamanders, among others.