EVOLUTION OF ELEPHANTS 



813 



Like the horses, the elephants probably originated from that 

 primitive ungulate group, the Condylarthra. The earliest known 

 form exhibiting proboscidean characters is Mreritherium, a 

 tapir-like animal whose remains have been found in the Middle 

 and Upper Eocene deposits of 

 the Egyptian Fayum. This was 

 a comparatively small creature, 

 about as large as a Newfoundland 

 dog. It probably differed but little 

 from other primitive ungulates, 

 but the skull (Fig. 159, 1) already 

 shows marked proboscidean ten- 

 dencies. The position of the nasal 

 bones, away back from the tip of 

 the snout, indicates that there 

 was in all likelihood a short pro- 

 boscis. The occipital region of 

 the skull is beginning to grow up 

 and air cells are beginning to 

 develop in the bones. The second 

 pair of incisor teeth in each jaw 

 are enlarged to form small tusks 

 and the hinder cheek teeth are 

 beginning to show an increase in 

 complexity of structure. The total 

 number of teeth however (86) is 

 only eight short of the full typical 

 mammalian dentition. 



The next stage is represented 

 by Palaeomastodon (Fig. 159, 2) 

 from the Upper Eocene of the same 

 region, some species of which were 

 little larger than Moeritherium 

 while others attained almost 



elephantine proportions. In this genus we notice a strong 

 accentuation of the proboscidean characters. The occiput is higher, 

 the nasal opening in the skull further back, the upper tusks 

 better developed, the cheek teeth more complex ; while the canines 

 and all the incisors except the tusks in both jaws have dis- 

 appeared. It will be observed that as yet there is no shortening 

 of the jaws, but, on the contrary, the lower jaw has become 



ivhitneyi, x i- (From Lull.) 



