SUBORDER D 



ARTIODACTYLA 



171 



point also become accelerated in the ontogeny of the highest forms of the 

 even-toed ungulates. 



Taking the dentition as a basis, the Artiodadyla fall into three principal 

 tribes : Bunodontia, Bimoselenodontia and Selenodontia. Through transitional 

 forms (such as Dicliohunidae), however, these are related to each other, and 

 may be separated into fifteen families, as follows : 



1. Bunodontia. 



1 . Suidae. 



2. Leptoi'lioeridae. 



3. Hippopotamidae. 



2. Bunoselenodnntia. 



1. Anthracotheriidae. 



2. Anoplotheriidae. 



3. Dicliohunidae. 



3. Selenodontia. 



1 . Xij)hodont.idae. 



2. Caenotheriidae. 



3. Agriochoeridae. 



4. Camelidae. 



5. TragvMdae. 



6. Hyperlragulidae. 



7 . Cervicornia. 



8. Antilocapridae. 



9. Cavicornia. 



Tribe 1. BUNODONTIA. 



Family 1. Suidae Gray. Swine. ^ 

 Dentition complete, hradiijodont and bunodont. Dental formula : 



3-2.1.4-3.3. 



3. 1.4-3.3. 



Superior and inferior molars with four obtuse conical low tubercles and frequently 

 numerous wartlike accessory comdes. In the oldest genera a fifth tubercle (protocomde) 

 present, or premolars less complex than molars. Canines very strongly protuberant. 

 Carpals and tarsals not coalesced. Posterior half of astragalus shifted sometvhat 

 laterally toward the superior portion. Feet tetradactyl, rarely two-toed. Metapodials 

 generally quite distinct. Lateral digits more slender and shorter than median ones. 



The Suidae are very closely allied to the Anthracotheriidae, at least in 

 their oldest types, and may have arisen from the same stem. Their living 

 representatives are now indigenous in Europe, Asia, Africa and America. 

 Fossil Suidae first appear in the Eocene of Europe, yet the greatest develop- 



FiG. 229. 



Cebochoerus minor Gervais. A, Upper fourth premolar and molars. Bolmerz, Egerkingen. i/i- (After 



Riitimeyer.) B, Lower cheek teeth. Pliosxjhorites, Quercy. Vi- (After Gaudry.) 



ment of this family occurs in the Miocene, Pliocene, Pleistocene and Recent. 

 In the New World they are less abundantly developed. 



Eohyus Marsh. A doubtful form, imperfectly known. Eocene ; AVyoming. 



Cebochoerus Gervais (Figs. 229, 230). Upper canines vertical, dagger-like, 

 lower canine developed as fourth incisor, and first premolar as canine. First 



1 Peter.Hon, 0. A., Memoirs of the Carnegie Museum, vol. ii., 1905 ; vol. iv., 1909.— Scott, 

 W. B., The Osteology of Elotheriuni. Trans. Amer. Phil. Soc, 1898, p. 273.— Steklin, H. G., 

 Geschichte des Suidengebisses. Abh. Schweiz. Pal. Ges., 1899, 1900. 



