620 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



/! 



terminal phalanges are obtusely rounded and not 

 deeply cleft distally, indicating the presence of 

 imperfect hoofs. Additional evi- 

 dence of water-loving or semiaquatic 

 habits is found in the weak spines of 

 the dorsal and lumbar vertebrae, 

 which are analogous to those in 

 Coryphodon and Metamynodon. The 

 dentition points to habits of feeding 

 on the succulent plants which are 

 characteristic of the borders of 

 streams. The skeleton as a whole 

 shows far more aquatic adaptations 

 than that of the tapirs. 



Palaeosyops major 



Palaeosyops major is represented 

 by some well-preserved limb bones 

 and a pelvis associated with the large 

 skull (Am. Mus. 13116) from Bridger 

 B 3. The large size of these bones, 

 coming as they do from so low a 

 level, is very noticeable. They even 

 exceed in total length those of P. 

 leidyi (Am. Mus. 1544), but the long 

 bones are more slender. The most 

 characteristic feature of the pelvis 

 (fig. 533) is the narrowness and ap- 

 parently uniform convexity of the 

 superior or anterior border of the 

 ilium as compared with its expansion 

 in subsequent stages of the develop- 

 ment of the titanotheres. This nar- 

 rowness is a primitive character, cor- 

 responding with the low geologic 

 level (Bridger B 3) at which this 

 specimen was found. Other chief 

 generic characters exhibited in this 

 skeleton are the following: Radius 

 (fig. 510) strongly arched forward 

 and having a deep groove for the ex- 

 tensor carpi radialis muscle; ulna 

 (fig. 511) without the incurved olecranon of MesatirJii- 

 nus; femur with a 

 straight, flattened 

 shaft, and a pa- 

 tellar groove pre- 

 senting anteriorly ; 

 tibia with an out- 

 curved cnemial 

 crest. The short- 

 necked astragalus 

 and the stout cal- 

 caneum are like- 

 wise of Palaeo- 

 syops type. 



The detailed 

 measurements of 

 this important skeleton as compared with the com 

 posite P. leidyi (fig. 536) are as follows: 



<fi)-\ 



\.maLv 



(as) 



Figure 534. — 

 Right femur and 

 tibia of Palaeo- 

 syops major 



Am. Mus. 131 16; Bridger 

 B 3. One-sixth nat- 

 ural size. 



Figure 535. — Astragalus and calca- 



neum of Palaeosyops major 

 Am. Mus. 13116; Bridger B 3. A, Left astragalus 



and calcaneum; B, left calcaneum with astragalus 



removed. One-third natural size. 



Measurements of skeletal parts of Palaeosyops major and P. 

 leidyi, in millimeters 



Femur, length 



Femur, distal breadth 



Femur, breadth across head and great 



trochanter 



Tibia, length (middle) 



Radius, length 



Ulna, length 



Astragalus, vertical inner face 



Astragalus, proximal width 



Calcaneum , vertical length 



Calcaneum, greatest width 



Mts II, length 



Mts III, length 



Mts III, distal width, transverse 



Pelvis, total length of os innominatum. 

 Pelvis, width of crest of ilium 



p. major, 



Am. Mus. 



13116 



(Bridger B 3) 



435 

 100 



127 



335 



280-290 



378 



61 



53 

 119 



63 

 126 

 136 



43 



448 



"220 



P. leidyi. 

 Am. Mus. 



(Bridger C, D) 



370 

 93 



132 



290 



235 



315 



57 



49 



97 



62 



102 



110 



42 



'46& 



'265 



» Estimated. ' Am. Mus. 2348. 



Palaeosyops leidyi 



Type locality and geologic horizon. — Bridger Basin, 

 Wyo.; Bridger formation, level Bridger C and D. 



Slceletal characters. — The first description and prelim- 

 inary restoration of the skeleton of this species (under 

 the name "Palaeosyops paludosus") was published by 

 Earle in his memoir of 1892 (1892.1, p. 314). In this 

 restoration the forefoot of Mesatirhinus was errone- 

 ously associated. (See fig. 86, p. 151.) 



The mounted skeleton of Palaeosyops leidyi in the 

 American Museum of Natural History (No. 1544) is a 

 composite one, reconstructed from a number of speci- 

 mens belonging to difl'erent individuals of at least two- 

 species {P. leidyi, P. robustus) and two geologic levels, 

 collected by the American Museum expedition of 1893 

 under Dr. J. L. Wortman. The well-preserved skull 

 and lower jaws, the cervical and first two dorsal verte- 

 brae, and the fore limbs down to the manus are from 

 one individual, an old male, No. 1544, the type of 

 P. leidyi. The scapulae, ribs, dorsals 4-11, 14-17, 

 caudals 8-10, and four sternals were supplied from 

 No. 1580. The right carpus, belonging to the prin- 

 cipal specimen (No. 1544), warrants the completion 

 of the rest of the feet from other specimens, cliiefly 

 No. 1550. The left hind limb was made up from 

 Nos. 1582 and 1562; certain of the dorsals and lum- 

 bars were supplied from Nos. 1593, 5177, 5158. The 

 foregoing specimens, after careful study, were found to 

 agree very closely in size and other characters, and 

 are probably all referable either to P. leidyi or to the 

 closely allied P. robustus. But the sacrum and pelvis, 

 No. 2348, from the Washalde Basin, are of somewhat 

 doubtful reference to this genus and may belong to 

 the genus Limnohyops. Certain remaining parts 

 (such as caudals 1, 2, 11-18, the right femur, the tibia 



