Chap. 35 



REPTILES FIRST LAND VERTEBRATES 



717 



Fig. 35.4. Tuatera {Sphenodon punctatum) has features of the early ancestral 

 reptiles (Cotylosaurs). A relic from a remote past, existing now only on the islands 

 near New Zealand. Length, 30 inches. (After Blanchard. Courtesy, Rand: The 

 Chordates. Philadelphia, The Blakiston Co., 1950.) 



the development and hatching of the eggs of birds and development and birth 

 in practically all mammals (Fig. 19.14). 



Like other land animals, reptiles do not go through an aquatic or larval 

 stage. Living upon the yolk and with the help of the other membranes the 

 reptile embryo like the bird embryo grows to relatively large size and inde- 

 pendence before it hatches (Fig. 35.2). As soon as they hatch, snakes take care 

 of themselves, much better than do chickens. 



Orders of Living Reptiles 



Modern reptiles are usually classified in either four or five orders, variously 

 arranged and named by different workers. In contrast to this small number are 

 the 14 or more orders of ancient ones known only by their fossil remains. 

 Modern reptiles include: 



Order Rhynchocephalia. Only one representative, Sphenodon, a lizard-like 

 connecting link between ancient and modern reptiles (Fig. 35.4). 



