Aiiimals Before Man 



bones was no thicker than a sheet of blotting 

 paper, though it was 2 inches in diameter and 

 something over 2 feet long. The entire skele- 

 ton, even when petrified, weighs but 5 or 6 

 pounds, and Professor Williston puts the weight 

 of the living animal at not more than 25 pounds. 

 The shoulder- joint that supported the big 

 wings of Ornithostoma was strongly and unique- 

 ly braced, being formed by a stout V-shaped 

 bone, which represents the two bones of a bird's 

 shoulder- joint known as coracoid and scapula. 

 In man, and all mammals save monotremes, the 

 shoulder- joint is formed by the shoulder-blade 

 only, and the coracoid is reduced to a little 

 process. The lower arm of the V was sup- 

 ported by the breast-bone, while the upper 

 rested against the back-bone, three joints of 

 which were united to give a firm point of at- 

 tachment. From the structure of Ornithostoma 

 it is entirely probable that it sailed, and did not 

 fly, by strokes of the wings, and the long tooth- 

 less beak, strong neck, and remains of fishes 

 found with its bones suggest that it lived on 

 fish. 



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