Class AvesBirds (Aves) are a group of vertebrates that have wings, feathers, hollow bones and numerous other adaptations for an aerial lifestyle.
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Class MammaliaThe highest class of vertebrata. The young are nourished for a time by milk, or an analogous fluid, secreted by the mammary glands of the mother. There are 3 subgroups: Placentalia (Bears) Marsupials (kangaroo) and Monotremes (platypus) which do not give birth to live young and are the only exceptions.
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