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