How are beavers mammals?
You already have good answers with characterizations of mammals. However, a characterization (i.e. a list of typical features) is not the same as a diagnosis (i.e. an accurate list of characters or combinations of these that only occur in a given taxonomic group). There are many other animals that are viviparous (live-bearing), as well as egg-laying mammals; similarly, other animals are homeotherm (warm-blooded), therefore these are not diagnostic mammalian traits. You can tell a mammal because it: – has hair/fur – feeds their young with milk – has a lower jaw formed by a single bone, the dentary – has 3 ossicles in the middle ear among other characteristics, for instance general complexity of the dentition that includes different types of teeth (incisors, molars, etc). Anyway, beavers qualify on the basis of these diagnostic characters.
