CHORD ATA — VERTEBRATA — REPTILES 



367 



Order g, Squamata 



Reptiles with an external 

 protection of horny scales 

 (whence the name, from 

 Latin 5^wawa/w5, scaly). The 

 quadrate bone is movably 

 articulated with the skull. 

 Limbs present or absent. 



This order, known from 

 the Triassic to the pres- 

 ent, includes the lizards 

 (Hmbs usually present and 

 adapted for walking), snakes 

 (with the long, narrow body 

 devoid of limbs) and pytho- 

 nomorphs (with a long snake- 

 like body and limbs modified 

 into swimming paddles). 

 The pythonomorphs, found 

 all over the world during the 

 Cretaceous, usurped the place 

 left by the declining sauropte- 

 rygians and ichthyopterygi- 

 ans ; some of these, as 

 Mosasaurus of North Amer- 

 ica and Europe, attained a 

 length of fifty feet and more 

 (Fig. 159). These aquatic 

 forms developed probably 

 from the semi-aquatic aigial- 

 osaurs of the Comanchean 

 and these in turn from the 

 terrestrial varanoids of the 

 Upper Jurassic. 



