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The Mammalia, colloquially known as mammals, is the class of animals primarily characterized by the presence of mammary glands in the female which produce milk for the nourishment of young (mamma is Latin for breast); hair; "warm blood"; and live birth of young.
There are a few mammals--the monotremes--that lay eggs and do not have mammary glands, but they do produce milk for their young. (Live birth also occurs in a variety of non-mammalian species; it is not a diagnostic characteristic for class mammalia.)
Kingdom Animalia, Phylum Chordata, Class Mammalia
- Order Multituberculata - extinct
- Subclass Monotremata (older name Prototheria) (platypus, echidna)
- Subclass Marsupialia (older name Metatheria)
- Order Didelphimorphia
- Order Paucituberculata
- Order Microbiotheria
- Order Dasyuromorphia
- Order Peramelemorphia
- Order Notoryctemorphia
- Order Diprotodontia
- Subclass Placentalia (older name Eutheria)
- Order Xenarthra (anteater, sloth, armadillo; formerly called Edentata)
- Order Pholidota (pangolin)
- Order Chiroptera (bat)
- Order Dermoptera (flying lemur)
- Order Primates (ape, monkey, lemur, human)
- Order Scandentia (tree shrew)
- Order Macroscelidea (elephant shrew)
- Order Rodentia (mouse, rat, squirrel, porcupine, beaver)
- Order Lagomorpha (hare, rabbit, pika)
- Order Insectivora (shrew, mole, hedgehog)
- Order Creodonta - extinct
- Order Carnivora (dog, wolf, cat, bear, weasel, seal, walrus)
- Order Condylarthra - extinct
- Order Artiodactyla (pig, deer, cattle, goat, sheep, camel)
- Order Cetacea(whale, dolphin, porpoise)
- Order Tubulidentata (aardvark)
- Order Perissodactyla (horse, tapir, rhinoceros)
- Order Hyracoidea (hyrax, dassie, agouti)
- Order Proboscidea (elephant)
- Order Embrythopoda - extinct
- Order Demostylia - extinct
- Order Sirenia (manatee, dugong, sea cow)
Therapsids are the direct ancestors of mammals, but some scientists consider them to be mammals.
In this case, Pelycosauria are the direct ancestors of mammals.
The names Prototheria, Metatheria and Eutheria expressed theory that Placentalia were descendants of Marsupialia, which were in turn descendants of Monotremata. Because this theory has been refuted, these names are rarely used nowadays.