A comparative study of the dentition of some common mammals

Abstract

Introduction: It is perhaps only natural that one who has made no special study of animal life, fails to realize fully the importance of the dental system. Not only are the teeth of animals vital to the species but also in many cases are they absolutely essential to the life of the individual. This of course is the most important factor in the consideration of the economy of teeth but not alone in this respect are they important. From the naturalist’s point of view, the dental system furnishes a very valuable and often the only means of classification and identification of animals both living and extinct. To go into this subject to any great depth one must first be thoroughly acquainted with the types with which he is dealing and even then, to make an exhaustive and scientific treatise on the subject one must give it close study and close observation for years. Therefore, in this necessarily brief discussion, we will confine ourselves to the working out of the most striking variations and peculiarities found in a few types with which we are most familiar. In only a few mammals are teeth entirely absent. In the whalebone whale the germs are found in the embryonic state but they never rise above the gums and disappear entirely before birth. The ant eaters and pangolins are examples of a few species in which no teeth are present in any stage. The young duck-bill has well developed molars but these have entirely disappeared in the adult animal. In many of the lower vertebrates the gradations from the horny skin of the head and jaws into well-defined teeth gives evidence of the nature of those organs and is sufficient, were no other evidence available, to classify teeth as modified dermal organs. Although they are present in many of the lower vertebrates, it is only in the mammals that they reach their highest development and are found definite in numbers, conformation and arrangement. In mammals these characteristics are comparatively fixed for any given species but in the different species we find wide variations.