Evolution of the mammalian tongue has been characterized by a number of extensive structural adaptations for the highly specialized functions which various tongues perform. Variations in shape, epithelium, muscle arrangement and mechanisms of lingual stiffening are described, and the possible way in which such changes have occurred is discussed. The review also shows that a study of the tongue's structure in conjunction with other anatomical features may serve as a useful indicator of an animal's habits and diet and provide important information for taxonomic purpose.