98 



WATER REPTILES OF THE PAST AND PRESENT 



Fig. 46. — ^Pectoral girdle of Nothosaurus, from 

 photograph by E. Fraas: id, interclavicle; cl, 

 clavicle; sc, scapula; cor, coracoid. 



The Nothosauria were much smaller reptiles than the plesio- 

 saurs, none of them perhaps exceeding the size of the smallest known 

 plesiosaurs. They were semiaquatic in habit, with many curious 



resemblances to other 

 semiaquatic reptiles of 

 a later time known, as 

 the dolichosaurs. The 

 neck is more or less 

 elongated, having about 

 twenty vertebrae in the 

 longest-necked forms; 

 the body is moderately 

 long, and broad, and 

 the tail is relatively 

 short. The vertebrae 

 and ribs are quite like 

 those of the plesiosaurs, 

 that is, the vertebrae 

 are gently concave at 

 each end, and the dorsal ribs are attached by a single head to the 

 transverse process high up on the arch; the cervical ribs are double- 

 headed, precisely like those of the older plesiosaurs, one of the char- 

 acters which insistently proves 

 the relationships of the two 

 groups. The bones of the shoul- 

 ders (Fig. 46) also have many 

 resemblances to the extraor- 

 dinary ones of the plesiosaurs, 

 though they are much less 

 specialized. There was no 

 sternum; the coracoids are 

 large, though very much 

 smaller than those of the plesi- 

 osaurs. The collar-bones are large and strong, joining each other 

 in front of the coracoids and firmly united with the shoulder- 

 blades at the outer extremity. Four vertebrae are united to form 

 a sacrum, and their union with the hip bones (Fig. 47) was much 



Fig. 47. — Pelvic bones of Nothosaurus: 

 it, ilium; ac, acetabulum; p, pubis; is, 

 ischium. (After Andrews.) 



