Mammals are a lade of endothermic amniotes distinguished from the reptiles and the birds by the possession of hair there middle ear bones, mammary glands in females, and a neo-cortex. The mammalian brain regulates body temperature and the circulatory system including the four-chambered heart. The mammals include the largest animals on the planet and some other whales, as well as some of the most intelligent. The encyclopedia presents a comprehensive synthesis of mammalian morphology anatomy physiology embryology and origin and evolution This encyclopedia provides a nucleus around which the teachers can plan a successful course without too much learning on complementary and supplementary readings Efforts have been made to avoid overburdening the students with information The book contains the reading material in the light of latest researches and development in the field These include origin and evolution of mammals, aquatic adaptation in Contents: Introduction Mammal Classification; Evolution of Elephant.