EVOLUTION OF THE SKELETON OF EOCENE AND OLIGOCENE TITANOTHERES 



645 



Comparative measurements oj the supposed hind feet of Metarhinus 

 sp., in millimeters 



Juvenile skeleton. — A skeleton of a newly born or 

 fetal animal, from Uinta B 1 (formerly called Uinta 

 upper A) was described in 1914 by Peterson (1914.2) 

 under the name Heterotitanops parvus. It consists 

 (fig. 578) of the greater part of the skeleton (Carnegie 

 Mus. 2909) including the skull and lower jaw, lacking 

 only the feet. As noted in Chapter VI (p. 426) the 

 skull and deciduous dentition of this animal present 

 important indications of relationship with some of the 

 smaller Dolichorhininae, presumably Metarhinus. 



The vertebral formula, according to Peterson, is 

 approximately as follows: Cervicals 7, dorsals 16 or 

 17, lumbars 3 (?), sacrals 4 or 5, caudals 14 or 15. 

 This may therefore be practically the same as in Doli- 

 chorhinus — namely, cervicals 7, dorsals 17, lumbars 

 4 (?), sacrals 4. 



The anterior face of the sacrum is quite even with 

 the supra-iliac border of the pelvis, a characteristic of 

 the titanotheres generally. The thoracic cavity was 

 of large size, as indicated by the rather long ribs. 

 There are apparently six bones in the sternum. The 

 scapula is titanotheroid in its general outline, the 

 spine being less overhanging than usual, which is 

 probably a juvenile character (Peterson). The other 

 limb bones are in a very immature condition but so 

 far as preserved suggest the limb proportions of Uinta 

 Basin titanotheres (Peterson). 



Dolichorhinus 



GEOLOGIC HORIZON AND GENERAL FEATURES 



These peculiar long-skulled, short-footed animals 

 are known only from the Eohasileus-DolichorTiinus zone 

 (Washakie B 2 and Uinta B 2). They are readily 

 distinguished by their very long skulls, and so far as we 



know they had short necks and relatively short, heavy 

 limbs. As they are partly adapted in the skull and den- 

 tition to grazing habits we should expect to find them 

 long-legged, or subcursorial, but they were not. The 

 fortunate discovery in Washakie B 2 of a specimen of 

 D. hyognathus (Am. Mus. 13164), in which the skull 

 and parts of the skeleton are associated, proves that 

 the hind foot of Dolichorhinus was brachypodal 

 (fig. 585). The contemporary perissodactyls of similar 

 size are Manteoceras and Sphenocoelus (an aberrant 

 titano there). Another contemporary is the peculiar 

 rhinoceros Amynodon, which is readily distinguished 

 by its long, slender feet. 



SKELETONS REFERRED TO DOLICHORHINUS HYOGNATHUS 



Materials. — Our knowledge of the skeleton of D. 

 hyognathus is very slight; it is based chiefly on remains 

 of two individuals. The first American Museum 



Figure 576. — Left scapula of 

 Metarhinus? sp. 



Am. Mus. 1873; Uinta B 1. One-sixtli 

 natural size. 



Ai '^'A2 



Figure 577. — Left radius and 



ulna of Metarhinus earlei ? 

 Am. Mus. 2363; Wasliakie B 1. Ai, 

 Outer side view; A2, front view. One- 

 sixth natural size. 



specimen (No. 1843) was found by Mr. O. A. Peter- 

 son in 1894, in horizon B 2 of the Uinta Basin, Utah. 

 It consists of a nearly complete vertebral series, a 

 part of the pelvis, the anterior part of the skull, the 

 humerus, and one rib. The second specimen (Am. 

 Mus. 13164) was found by Mr. Paul Miller in 1906, in 

 Washakie B; it consists of the finely preserved skull 

 already described, with which were associated parts 

 of the atlas and axis, one lumbar, parts of the scapula, 

 the humerus, the proximal half of the ulna-radius, the 

 femur, two metatarsals, and isolated foot bones. 

 Another specimen also found in Uinta B 2 (Am. Mus. 

 1836) consists of parts of the radius and ulna, associ- 

 ated with the jaw. An atlas (Am. Mus 1837) was 

 found associated with the skull of D. intermedius. 

 A number of other bones not associated with cranial 

 material have been referred to this genus, especially an 

 atlas (Am. Mus. 1844); also a part of the scapula 

 (Am. Mus. 1833) and a radius and ulna (Am. Mus. 

 1831). The manus, unfortunately, is not known. 

 The materials above enumerated enable us to make a 



