4<h REPTILES xv. 7- 



are insectivorous and carnivorous. They live in burrows, often in 

 association with petrels. The eggs take over a year to hatch. 



Sphenodon evidently shows us a type that has departed relatively 

 little from the condition of diapsids in the late Permian. Yet its appear- 

 ance, habits, and soft parts are very like those of lizards, and provide 

 us with evidence that these animals remain in essentials rather close 

 to the original amniote populations. A few other extinct rhyncho- 



itf. fr. 



Fig. 231. Skull of Sphenodon. Lettering as Fig. 214. (After Romer, 

 Vertebrate Paleontology, Chicago University Press.) 



cephalians are known; these include the rhynchosaurs, in which the 

 tip of the upper jaw had a hooked beak-like appearance. 



8. Order Squamata 



The lizards and snakes are the most successful of modern reptiles, 

 numbering between them over 5,000 species. Probably the groups 

 arose from eosuchians related to *Prolacerta. Such forms would also 

 have been close to the Rhynchocephalia, differing from them, however, 

 in a tendency to lose the lower temporal arch and to develop a movable 

 quadrate. 



It has now been shown that the lizards are a more ancient group 

 than was formerly supposed, and had appeared by the end of the 

 Triassic. Furthermore, some of the early forms were already con- 

 siderably specialized. Our knowledge of the early lacertilian radiation 

 is still incomplete, however, and none of the existing lizard families 

 are known much before the Cretaceous. The earliest undoubted snake 

 occurs in the upper Cretaceous and the group does not seem to have 

 become abundant until the Oligocene. 



