600 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Only three scapulae are known, as follows : (1) Medi- 

 portal, Dolichorhinus longiceps (figs. 509, 582); (2) 

 subgraviportal, Palaeosyops (figs. 509, 545), with. 



In Mesatirhinus we should expect to find the scapula 

 proportioned somewhat like that in Tapirus; unfor- 

 tunately this scapula is unknown. 



i'lGUUE 5Ui. Restoration of Eotilanops borealis 

 Modeled by E. S. Christman. About one-twelfth natural size 



height 345 millimeters, breadth 260; (3) supposed 

 MetarUnus (figs. 509, 576, Am. Mus. 1873, Uinta B), 

 elongate compared with that of Palaeosyops — namely, 

 length 265 millimeters, breadth 165 (estimated). The 

 supposed MetarJiinus may be taken as the mediportal 

 type; it is less expanded toward the upper border. 



HUMERUS 



We hare observed (fig. 510) that the characters of 

 the humerus of the titanothere family are rapidly 

 intensified by adaptation. Each genus exhibits dis- 

 tinctive ratios of length of the humerus and radius, as 

 shown in the accompanying table. 



Measurements of fore limh of certain titanotJieres compared with tapirs, in millimeters 



Eadio- 



humeral 



ratio 



Metacarpo- 



humeral 



ratio 



Tapirus terrestris 



Tapirus indicus 



Eotitanops princeps (borealis), T^m. Mus. 296 



Limnohyops? monoconus. Am. Mus. 11689 



Palaeosyops leidyi, Am. Mus. 1544 



Palaeosyops copei?. Am. Mus. 12205 



Dolichorhinus h3'0gnathus, Am. Mus. 13164.. 



Menodus trigonoceras, Munich Mus 



Brontops robustus, Yale Mus. 12048 (type).. 

 Brontops sp., Am. Mus. 518 



205 

 250 

 203 

 293 

 325 

 340? 

 ■315 

 620 

 608 

 528 



177 

 228 



228 

 235 

 237 

 '284 

 520 

 504 

 478 



77 



72 



69? 



81? 



83 



82 



90 



106 

 120 

 85 

 109 

 113? 

 106 



50 



48 



41 



37 



34? 



30 



240 

 230 

 214 



38 

 37 

 40 



It wUl be observed that ia Palaeosyops and DolicJio- 

 rliinus the humerus is much longer than the radius. 

 These are subgraviportal types, but even in the medi- 

 portal Limnohyops the humerus is somewhat longer 

 than the radius. 



It is, however, a very marked distinction of the 

 titanotheres, already pointed out, that as they become 

 heavier the radius elongates more rapidly than the 



humerus. Thus the radiohumeral ratio rises from 72 

 in Palaeosyops leidyi to 90 in Brontotherium gigas. 



The rugose muscular attachments of the humerus 

 rapidly assume progressive graviportal characters, 

 which even in the lower Bridger enable us to distin- 

 guish readily the titanothere humerus. These char- 

 acters are strengthened in the Oligocene titanotheres 

 and were undoubtedly correlated with certain dis- 



