THE MUSCULAR ANATOMY AND THE RESTORATION OF THE TITANOTHERBS 



709 



noceroses. The construction of the jaws and grinding 

 teeth indicates that their main food was very coarse 

 herbage, rather than grass, so it is reasonable to sup- 

 pose that the mobile lips would be adapted rather to 

 browsing and tearing up shrubs than to cropping 

 short grass, and consequently that the median part 

 of the lips would be pointed and very protrusile, 

 somewhat as in the black rhinoceros, rather than 

 truncate, as in the grazing lips of the white rhinoceros 

 and horse. 



Such being our conceptions of the first and of the 

 last known members of the family, it seems reasonable 

 to assign the middle Eocene genus Manteoceras (in 

 which the bones and teeth were structurally interme- 



SECTION 3. MUSCLES OF THE NECK AND BACK 



In the following pages we have attempted to deter- 

 mine what muscles and ligaments were attached to 

 the principal parts of the skeleton; hence the subject 

 matter is classified primarily according to the topog- 

 raphy of the skeleton, secondarily according to 

 musculature. 



The vertebrae of titanotheres are sufEciently like 

 those of the horse to indicate that the axial muscula- 

 ture was also essentially similar. The following de- 

 scription is based largely on Schmaltz's (1909.1) figures 

 of the cervical and dorsal musculature of the horse 

 supplemented from photographs by Herbert Lang of 

 a dissected white rhinoceros. 



Figure 646. — Models of half of the skuU and head of Eoiitanops borealis (A) and Manteoceras 



manteoceras (B) 

 Modeled by E. S. Christman under the direction of William K. Gregory. One-eighth natural size. 



diate between these extremes) to an intermediate stage 

 in the development of the nose and lips (figs. 646-649). 



The restoration of the fore part of the head of the 

 upper Eocene Protitanotherium emarginatum is based 

 upon the well-preserved facial bones and lower jaw of 

 the type and is probably fairly accurate, but the 

 restoration of the back part of the head is hypothetical. 



In Figure 647 we give another series of restorations, 

 showing the heads of members of the principal genera 

 of middle and upper Eocene titanotheres, except the 

 Palaeosyopinae, and showing also the contour of the 

 skull. 



The occiput (fig. 650), especially in the later titano- 

 theres, bore highly rugose crests, which probably 

 separated the jaw muscles (temporals) from the neck 

 muscles and were covered with thick, tough skin. A 

 deep median pit marks the insertion of the ligamentum 

 nuchae. The semispinalis capitis (complexus) was 

 probably inserted just beneath the occipital crest and 

 lateral to the ligamentum nuchae. The splenius was 

 lateral to the semispinalis and probably formed a 

 wide sheet just behind the lateral occipital ridge. 

 Below the splenius and behind the auditory meatus 

 was the insertion for the tendon of the longissimus 



