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Types of Mammals

In biological classification, mammals form one of the six major classes of vertebrate animals. Mammals themselves are divided into three different groups, or subclasses, based on distinctive underlying features: Monotreme, Marsupial, and placentals.

Most large predatory land mammals belong to a group called the carnivores, which contains about 240 species. Some of these animals, such as lions and wolves, rarely eat anything apart from meat, but others, especially bears, have a more mixed diet. Mixed diets are also common in a different group of mammals—the primates. Primates include animals such as lemurs, monkeys, apes, and humans, and most of the 230 species live in trees.

The world's large plant-eating mammals are divided into two major groups. One group, called the artiodactyls, contains animals such as pigs, deer, cattle, and antelope, which have hoofed feet with an even number of toes. The other, a much smaller group called the perissodactylas, includes horses, tapirs, and rhinoceroses, which have an odd number of toes.

Some mammals have adapted to life in the water. The seals, including sea lions and walruses, can sleep and feed in the open ocean but must return to land in order to reproduce. Manatees and dugongs are large, plant-eating mammals that spend their entire lives in the water. The whales, including the huge baleen whales and the dolphins, are well adapted as fast, open-ocean predators. Still, like all other mammals, aquatic mammals would drown if they could not reach the surface to breathe.