THE MXJSCULAR ANATOMY AND THE RESTORATION OF THE TITANOTHERES 



715 



The high deltopectoral crest gives attachment to the 

 teres minor and below this is produced into a large 

 reflected protuberance for the deltoid. The rough 

 anterior border of the deltopectoral crest probably 

 gave origin for a branch of the cephalohumeralis. 

 Windle and Parsons (1901.1, p. 679) state that this 

 muscle is a combination of the anterior part of the 

 trapezius, the cleidomastoid, and the clavicular part 

 of the deltoid. 



The lower extension of the deltopectoral crest very 

 probably gave attachment to the pectoralis super- 

 ficialis (p. major) and below this to the cephalohume- 

 ralis. The posterior upper border of the deltopectoral 

 crest probably gave attachment to the external head 

 of the triceps. 



behind and below it was attached the medial head of 

 the triceps. 



From the entocondyle arose the medial or humero- 

 radial collateral ligament and the several flexors of 

 the forearm. 



Above the olecranal fossa is an area which was 

 probably for the so-called anconeus; this muscle in 

 ungulates appears to represent a fourth head of the 

 triceps. 



MUSCULAR ATTACHMENTS OF THE RADIUS 



The head of the radius was flattened and appressed 

 to the ulna, and the radio-ulnar facets permitted only 

 a very slight degree of supination. In correlation 

 with this the tubercle (fig. 654, tub.) was greatly 

 reduced and no longer served as the chief insertion 



Figure 653. — Left humerus of Broniops robusius (type), showing probable position and attachments of 



principal muscles 

 Ai Front view; Ar, back view; A3, outer side view; Ai, inner side view. One- eightli natural size. 



The extensive winding surface for the brachialis 

 anticus on the back of the humerus passes from above 

 downward and forward; it lies behind the deltoid 

 crest. Below the brachialis anticus area and above 

 the supinator crest arose the powerful supinator 

 longus and extensor carpi radialis. 



From the region of the ectocondyle arose the humeral 

 slip of the extensor communis digitorum, the external 

 collateral ligament, and the extensor carpi ulnaris, 

 which in ungulates serves as a flexor of the forearm. 



On the inner or costal side of the humerus we observe 

 especially the attachment for the subscapularis (into 

 the lesser tuberosity) and the latissimus rugosity for 

 the common tendon of the teres major and latissimus 

 dorsi. Below and in front of the latissimus rugosity 

 is the insertion area for the coracobrachialis, while 



point for the tendon of the biceps; this tendon was 

 probably inserted chiefly on the front of the head .of 

 the radius and may also have extended around to 

 the inner side, as in Tapirus and Equus. 



On the inner or medial surface of the radius about 

 2 inches below the proximal end is a rugose area which 

 is probably for the insertion of the medial collateral 

 ligament. Below this, in the middle third of the 

 shaft and partly on the front surface, is a vertically 

 extended rugosity which was probably, as in Rhino- 

 ceros, the attachment area of the brachialis anticus. 

 At first sight the rugosity in question seemed to be for 

 the pronator radii teres, as in carnivores, but in the 

 tapir and apparently also in Palaeosyops the tendon 

 of this muscle extended down the whole inner edge of 

 the radius. (Murie, 1872.1; Turner, 1850.1.) 



