EVOLUTION OF THE SKELETON OF EOCENE AND OLIGOCENE TITANOTHERES 



651 



The manus. — The manus of the specimen under description is 

 complete with the exception of the ungual phalanges and the 

 proximal phalanges of digits III and IV, which were not re- 

 covered. The foot as a whole is short and broad, and, when 

 compared with the manus of Eoiitanotherium, it may be said to 

 be heavier. In comparing the carpal elements of the two 

 genera it is at once observed that they are all of greater height in 

 the present genus than in Eotilanotherium. 



Left astragali of Dolichorhinus and allied types 



Front (Ai, etc.) and rear (.A2, etc.) views. A, MesaliTMnusf, Am. Mus. 2352, Washakie B? (of. figs. 

 569, 670, 572) ; B, Dolichorhinus hyognathus?, Am. Mus. 1846, Uinta B 2 (probably associated with 

 a skull of Dolichorhinus sp.) ; C, Dolichorhinus?, Am. Mus. 1838, Uinta B 2; D, Tdmatheriumf, 

 .-im. Mus. 1962. Uinta B 2. One-third natural size. 



The metacarpals, in proportion to the carpals, are shorter than I 

 in Eotiianoiherium. The metapodial keel of Mtc II is less | 

 oblique to the long axis of the 

 bone than that in Eoiitanoiherium, 

 otherwise the differences between 

 these two genera are slight. The 

 liead of Mtc III differs from that 

 in Menodus by having the ulnar 

 portion more squarely truncated 

 and by the much smaller size of 

 the facet for Mtc II on the radial 

 angle. Mtc IV presents only 

 slight differences from the corre- 

 sponding bone in Oligocene titano- 

 theres. In its general details Mtc 

 V is quite similar to the same 

 bone in Eoiitanotherium but pro- 

 portionally shorter. 



There are considerable variations in the length of the limb of 

 the genus Dolichorhinus. The humerus and the radius and 

 ulna of specimen No. 1961 ^s in the American Museum very 

 nearly agree in general length with those of No. 2865 in the 

 Carnegie Museum, while the fore foot of the former specimen is 

 considerably longer than in the latter.^' On the other hand, the 

 specimen No. 13164 (Am. Mus.) from the ?Washakie B level 

 indicates that the humerus is relatively longer and the fore foot 

 shorter than in the fore limb of Dolichorhinus in the 

 Carnegie Museum, which is described in this paper. 



In conclusion this Carnegie Museum skeleton shows 

 that Dolichorhinus had a relatively shorter and wider 

 manus than that of Mesatirhinus — that it was in fact 

 almost brachj'podal.'"' 



SKELliTON OF DOLICHORHINUS LONGICEPS IN THE 

 FIELD MUSEUM 



The skeleton of Dolichorldnus longiceps in 

 the Field Museum (No. 12200), from Riggs's 

 "upper Metarhinus beds" ( = upper part of 

 Uinta B 1), comprises a well-preserved skull 

 and jaws associated with a vertebral column 

 which is complete from the atlas to the last 

 sacral vertebra; together with the left scapula, 

 both humeri, the left radius and ulna, and the 

 complete pelvis. 



This important skeleton furnishes the proof 

 that in Bolichorhinus longiceps there were 21 



-Ai 



Figure 589.- 



^2 ^3 



-Cervical vertebrae of Dolichorhinus longiceps? 



Carnegie Mus. 2865. Ai, Left side of atlas; Aj, anterior view of atlas; As, left side of axis. 



natural size. 



Measurements of Dolichorhinus longiceps (by Peterson) 



Millimeters 



Total length of scapula 337 



Total length of humerus, head to distal end 285 



Total length of ulna 340 



Total length of radius '. 295 



Total length of manus, approximately 200 



Height of carpus at unciform and cuneiform 59 



Transverse diameter of carpus at proximal row of carpals 90 



Greatest length of Mtc II 116 



Greatest length of Mtc III 124 



Greatest length of Mtc IV 109 



Greatest length of Mtc V 95 



As in Eotitanoiherium and the titanotheres generally, the 

 phalanges are short, broad and depressed. In comparing 

 Osborn's restoration of Dolichorhinus (fig. 579) with the above- 

 described fore limb it appears that the foot of the present speci- 

 men is shorter, while the radius, ulna, and scapula are longer. 



dorsolumbar vertebrae, 17 dorsals and 4 lumbars. 

 In the preliminary reconstruction of Dolichorhinus 



33 The dimensions of the metacarpals of this specimen in millimeters as measured 

 by W. K. Gregory are a»s follows; 



'^ The manus referred to, Am. Mus. 19G1 (fig. 587), is probably referable to Amyno- 

 don sp. Its resemblances to Dolichorhinus, however, are remarkably close. 



■"' Peterson's final illustrations of the manus of D. longiceps (Carnegie Mus. Mem., 

 vol. 9, pi. 54, 1924) show that it is strikingly similar to that of Mesatirhinus, only 

 somewhat broader. Mtc III is relatively longer and narrower than Mts II. The 

 manus as a whole is of the compressed, straight-sided type, presenting a great 

 contrast to the spreading manus of Palaeosyops. 



