744 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



1. In the mediportal ilium of Tapinis cc (tuber 

 coxae) corresponds broadly with the primitive anterior 

 border of the ancestral ilium of the unguiculates and 

 condylarths (A). It serves chiefly for the attach- 

 ment of the obliquus abdominis externus and o. a. 

 internus muscles. 



3. As compared with the even border of the unguicu- 

 late, creodont, or condylarth ilium the raised border 

 ss (tuber sacrale) appears to be a neomorph, or 

 secondary upgrowth of the suprasacral border of the 

 ilium, designed on the dorsal fossae for the expansion 

 of the gluteus medius and longissimus dorsi muscles, 



Figure 674. — Adaptive forms of ilia and sacral attachment 

 Ai-A', Mediportal (Ai, A^, Tapirus terrestris, juv.; A', the same, adult; AS T. indicus. adult); B, cursorial (,Eguus); C, subgraviportal (Manteoceras); 

 C, the same with sacrum; D, graviportal {Bhinoceros); E, cursorial (.Eangifer). S, Sacral attachment; S', suprasacral fossa; ss, tuber sacrale; 

 cc, tuber coxae; b, region between ss and cc. All two-filteenths natural size. 



2. The smooth, thin intermediate crista cs broadly 

 compares with the dorsal border of the primitive ilium 

 and is mainly for the insertion of the fascia of the 

 longissimus dorsi, a muscle which is much more 

 important in the ungulates than in the unguiculates. 



and on the ventral side for the ligamentous fixation of 

 the pelvis to the sacrum. The gluteus medius, with 

 its profound insertion in the great trochanter (f) 

 and third trochanter (t'") of the femur, is one of the 

 most important propellers of the heavy ungulate body. 



