THE ARTIODACTYL UNGULATES 211 



also the first Cavicornia appeared but they formed no exten- 

 sive group until the Pliocene when the number of species 

 greatly increased with Asia as a center of radiation. 



As regards origin we have previously seen that even in the 

 earliest examples the Artiodactyla are quite clearly distin- 

 guished from the Perissodactyla, that resemblances between 

 these two orders are the result of parallel or convergent evolu- 

 tion and that any heritages which they may possess in com- 

 mon are merely those derived from a protungulate stock. 

 Some authors have suggested a genetic relationship between 

 the primitive Artiodactyls and the Insectivores and Primates 

 but such similarities as occur are merely superficial and prob- 

 ably do not point to phylogenetic connections. Far more likely 

 is it that the Artiodactyla are originally related to unknown 

 Basal Eocene Creodonta which, however wide the difference 

 between modern Artiodactyls and this extinct and usually 

 carnivorous suborder, foreshadowed many of the features 

 found in the primitive Artiodactyla. In a previous chapter we 

 have noted that the fissipede Carnivores of today probably 

 arose from a family of Creodonts known as the Miacidag. The 

 Artiodactyl Ungulates have no connection with this family but 

 with another Creodont group, the Mesonychidae which were 

 animals developed for great speed, possessing broad blunt claws 

 and probably already vegetarian in habit. 



