South Dakota School of Mines 101 



while at the top there are never more than two on a side, often 

 only one. sometimes none. In skulls from the very lowest beds 

 the incisors have already become so rudimentary as to be no 

 longer functional. As would be expected, the number of in- 

 cisors decreased after they became of no functional value. In 

 the matter of incisors the Titanotheriidae at the time of their 

 extermination, were in a fair way to accomplish just what the 

 somewhat related, but more persistent, Rhinocerotidae have 

 nearly succeeded in doing, viz., the elimination of the incisor 

 dentition."* 



According to Hatcher, the Titanotheres had their origin 

 in early Eocene time, were of considerable importance through- 

 out the Bridger and Uinta periods, reached their culmination 

 during Lower Oligocene time, and became wholly extinct at 

 the close of the latter period. They present one of the most in- 

 teresting illustrations known of rapid evolution in size and 

 special characters followed by quick extinction. They developed 

 slowly at first, and although their ancestors may be traced for 

 perhaps half a million years, they seem to have left absolutely 

 no descendants. Outside of North America the Titanotheres 

 have been recognized only in the Balkan Mountains. 



During the time of their greatest development the Titano- 

 theres were the largest of all the mammals in the localities where 

 they lived. They were well prepared by size and offensive 

 weapons for combating the attacks of predaceous animals and 

 they were possessors of perhaps the most efficient dental 

 equipment ever developed for masticating coarse vegetable food, 

 such as evidently flourished in abundance in the region at that 

 time. Their size was comparable to that of the present day 

 elephant, averaging slightly smaller. 



Of the restorations that have been made, the earliest one, 

 tht skeleton of Titanotherium prouti from the Upper Titano- 

 therium beds described by Scott and Osborn in Bulletin Museum 

 Comparative Zoology, 1887, indicates an animal more than 

 twelve feet long and approximately eight feet high at the 

 shoulders. The skeleton of Megacerops robustus, Plate 35, from 

 the Upper Titanotherium beds, restored by Osborn and Wort- 

 man, 1895, measures thirteen feet, eight inches in length, seven 

 feet, seven inches in height, and breadth across the pelvis three 

 feet, ten inches. This would indicate an animal fourteen feet or 



*Hatcher, J. B. The Titanotherium Beds. Am. Xat., Vol. 27, 

 1893, pp. 204-231. 



