1. Monotremes: These are the most primitive mammals, characterized by laying eggs instead of giving birth to live young. Monotremes include platypus and echidnas.
2. Marsupials: These mammals are characterized by giving birth to underdeveloped young that are carried and nursed in a pouch. Marsupials include kangaroos, koalas, and opossums.
3. Xenarthrans: This group includes armadillos, sloths, and anteaters. Xenarthrans are characterized by having a bony armor or carapace.
4. Rodents: Rodents are the largest order of mammals, comprising around 40% of all mammal species. Rodents include mice, rats, squirrels, and hamsters.
5. Lagomorphs: This order includes rabbits and hares. Lagomorphs are characterized by their herbivorous diet and long ears.
6. Eulipotyphlans: These are small, insectivorous mammals, often called shrews and moles.
7. Dermoptera: This order includes flying lemurs. Dermoptera are characterized by their ability to glide.
8. Chiropterans: The chiropterans are the only mammals that can fly. This group includes bats.
9. Cetaceans: Cetaceans are fully aquatic mammals, including whales, dolphins, and porpoises.
10. Carnivorans: These are meat-eating mammals, including dogs, cats, bears, and seals.
11. Primates: Primates include humans, apes, monkeys, and lemurs. They are characterized by having hands with opposable thumbs and a highly developed cerebrum.