OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 215 



It is striking that no trace of monkeys has been found; in fact, there 

 is every evidence that these animals disai)poared from America at or before 

 the close of tlie Eocene. The 

 small, triangular teeth of Lepto- 

 chcerus, formerly referred to 

 the primates by INIarsh and 

 Cope, now prove to belong to 

 a primitive surviving artio- 

 dactyl family (Leptochoerida?). 

 Beside the leptochoerids the 

 artioclactyls include the giant 

 pigs or entelodonts, and pec- 

 caries or dicotylids, the foreign 

 anthracotheres, and the much 

 more numerous and varied 

 native oreodonts. 



Most important of all, the 

 hypertragulids appear, typified 



by the diminutive Hypertragulus and Leptomeryx. The former (Hypertra- 

 guliis) bears some resemblance to the chevrotains (Tragidus) of southern Asia. 

 Matthew's recent restudy ^ of Leptomeryx, a member of this family, brings 



Fig. 103. — Skull of the Lower Oligocene titano- 

 there Brontotherium gigas (male). In the American 

 Museum of Natural History. After Osborn. 



Fig. 104. — Contemporary Lower Oligocene manmials of South Dakota to same scale 

 (X x\;)- By Charles R. Knight. A. Leptomeryx, ancestral hornless deer. B. Oreodon, a 

 primitive browser or grazer. C. Hycenodon, the last of the creodonts. 



out the very important fact that it has numerous indications of remote 

 relationship to the true ruminants and especially to the American deer 



' Matthew, W. D., Osteology of Blastomeryx and Phylogeny of the American Cervidse. 

 Bull Amer. Mus. Nat. Hist., Vol. XXIV, Art. xxvii, 1908, p. 552. 



