A Pallid bat, common in California. It is a member of the class Mammalia. Despite the fact that it has wings, you can tell it is not a bird because it does not have feathers or lay eggs. It must be a mammal because it has fur (fish have scales, amphibians have moist skins with fur, reptiles have scales). This also tells you that it bears live young that it feeds with milk and that it is warm-blooded.