712 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



capitis, and below this in turn, near tlie lower end of 

 the mastoid process, was the insertion of the tendon 

 of the cephalohumeralis (cleidomastoideus). Beneath 

 the semispinalis and splenius is a wide nuchal surface 

 for the obhquus capitis superior, rectus posticus major, 

 and rectus posticus minor. The relations of all 

 these muscles to the cervical vertebrae are shown in 

 Plate XLIII. 



The rugose tips of the dorsal and cervical spines 

 served for the origin of the ligamentum supraspinale 

 and the ligamentum nuchae, the latter being inserted 

 into the tips of the cervical vertebrae and into the 



to the longissimus atlantis. Both had short branches 

 arising from the outer surface of the prezygapophyses 

 of successive vertebrae. Below the zygapophyses and 

 above the transverse processes were the intertransver- 

 sarii muscles, which also extended from one transverse 

 process to the next. The outer rugosity of the trans- 

 verse processes also bore the slips of the scalenus brevis 

 (primae costae), levator scapulae ("serratus cervicis"), 

 and cephalohumeralis. 



The infero-anterior processes of the cervical verte- 

 brae gave rise to slips of the longus colli, which, joining 

 with similar slips from the inferior faces of the centra. 



Figure 650. — Occiput of an Oligocene titanothere {Brontops robustus) , showing the probable general location 



and planes of the neck muscles 



The extremely rough occipital and lambdoidal crests were probably covered with tough skin, as in recent perissodactyls. The precise limits 

 of the insertion areas can not be determined. Two-ninths natural size. 



middle of the occiput (iig. 650). On the anterior edges 

 of the neural spines of the cervicals were inserted the 

 shps of the spinalis dorsi (cervicis). The sides of the 

 cervical spines carried the multifidus spinae, which 

 ran obliquely downward and backward to be inserted 

 above the posterior zygapophyses of the next succeed- 

 ing vertebrae. The outer dorsal rims of the post- 

 zygapophyses bore the slips of the semispinalis capitis, 

 which ran upward and forward, converging toward 

 and being inserted on to the nuchal surface, just 

 below the occipital crest and on either side of the 

 midline (fig. 650). Along the line of the prezyga- 

 pophyses and postzygapophyses ran both the longissi- 

 mus capitis, which was inserted into the posterolateral 

 margin of the lambdoidal crest behind the auditory 

 meatus, and the longissimus atlantis, which was 

 inserted into the edge of the transverse process of the 

 atlas. The longissimus capitis lay immediately dorsal 



ran forward and were inserted on the hypapophysis of 

 the atlas. 



The principal attachments of the muscles and liga- 

 ments of the presacral vertebrae are summarized 

 below. It is assumed that every homologous part in 

 the horse and the titanothere would carry a homo- 

 logous muscle and ligament attachment. The very 

 full data for such attachments in the modern horse 

 given by Schmaltz (1909.1) accordingly form the 

 chief basis of the determinations given. 



Principal attachmenis of the muscles and ligaments in the pre- 

 sacral vertebrae in the horse and the titanothere 



Muscle attachments of the atlas. (See PI. XLm) 



Neural spine (s) : rectus capitis posticus minor. 

 Transverse process (t), dorsal surface: obliquus capitis inferior. 

 Transverse process (t) , ventral surface : obliquus capitis superior. 

 Transverse process (t), e.xternal border: obliquus capitis 

 superior. 



