Regents of the University of Michigan
Animal Diversity Web: Mammalia
For an overview of the anatomy and characteristics of mammals, visit this Animal Diversity Website. Discusses characteristics not found in other animals, the function of their hair, and their production of milk.
Regents of the University of Michigan
Animal Diversity Web: Mammary Glands
A very solid history on the evolution of, and function of, the glands that give the group mammals their name. Good comparisons of other mammals and their function.