CHAPTER X 

 ELEPHANTS, HORSES, AND CAMELS 



The fossil remains of these three groups of vertebrates and their 

 ancestors are so abundant that they afford us an almost complete 

 record of the evolution of modern species since the Eocene. The 

 record is so remarkable that it has deservedly been described many 

 times, and has had unsurpassed influence in the establishment 

 of the theory of evolution. The first extensive series of fossils of 

 any of these animals was that assembled at Yale University, 

 largely through the efforts of Professor Marsh, to illustrate the 

 evolution of the Horse. This collection has been characterized 

 as the "first documentary record of the evolution of a race " (Lull). 

 It was regarded by Huxley as conclusive evidence of evolution, 

 and would have been visited by Darwin had his health permitted. 

 The fossil records now available afford many such examples of an 

 actual phylogenetic series, but none surpass that of the horses. 

 The records of elephants, horses, and camels are among the most 

 striking and complete that we have. 



Systematic Position. The three forms of animals are included 

 in three orders of Eutheria, the Pro]:)Oscidea, Perissodactyla and 

 Artiodactyla respectively. All belong to the section Ungulata, 

 the hoofed animals. The first order is characterized by the elonga- 

 tion of the nose and upper lip, the occurrence of five functional 

 digits on all feet, the development of the upper incisors into tusks, 

 and the highly developed grinding molars. The second order 

 represents a very different type of adaptation, although the animals 

 of both orders are herbivorous. The Perissodactyla have not 

 more than four digits on the front feet and not more than three on 

 the hind feet. In all species the third digit is the most important 

 and in the family Equidae, including the horses, asses and zebras, 

 the third alone is functional. Their teeth, like those of the ele- 

 phants, are ridged grinding structures, but are less extremely 

 speciahzed. The camels are speciahzed for life in arid regions. 

 They are even-toed ungulates, i.e., the feet retain hoofs on two or 



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