SAURO PTERYGIA 



99 



firmer than was the case with the plesiosaurs. The limbs are 

 elongated, but it will be observed in the figures (Fig. 48) that the 

 radius and ulna, tibia and fibula, that is, the bones of the forearm 

 and of the leg proper, are relatively very short as compared with 

 the humerus and femur, a sure indication of the beginning of 

 aquatic habits. The toes and fingers were doubtless webbed, and 

 there was no increase in the num- 

 bers of bones in the digits, so 

 conspicuous in the plesiosaurs. 

 The external nostrils are large, but 

 are not situated so far back near 

 the eyes as in the plesiosaurs. 

 There is a large pineal opening in 

 the top of the skull, as in the plesi- 

 osaurs, but no sclerotic or bony 

 plates have been observed in the 

 eyes. They had ventral ribs like 

 those of the plesiosaurs. 



No impressions of scales or 

 bony plates have ever been found 

 with the remains of the notho- 

 saurs, and it is the belief that the 

 skin was bare. A good idea of 

 their general appearance will be 

 gained from the accompanying 

 restoration adapted from that of 

 Professor Fraas (Fig. 44) and the 

 restoration of the less highly 

 specialized Lariosaurus , made 

 from a very complete skeleton in 

 the Frankfort museum (Fig. 49). 



It has been thought that these nothosaurs, so intermediate in 

 structure between the true plesiosaurs and land reptiles, were the 

 actual ancestors, but this is rather doubtful. It is probable that 

 they were only very closely akin to the real ancestors, since in some 

 ways they had become specialized too much, and, as we have 

 already explained, highly specialized characters or organs can never 



8 ' \\M m 



9 



1 \<b\ *i 



Fig. 48. — Legs of Lariosaurus bal- 

 samic an Upper Triassic nothosaur: h, 

 humerus; r, radius; u, ulna; i, inter- 

 medium; 11c, ulnare; /, femur; fi, 

 fibula; t, tibia; a, astragalus; c, cal- 

 caneum. (After Abel.) 



