STRUCTURE OF THE VERTEBRATES 



73 



During their evolution the orders of birds have developed a 

 wide number of adaptive radiations. Some are typically wading 

 animals with long legs and beaks, as in the cranes, storks and 

 flamingoes; others are adapted for swimming, as the ducks, 

 swans and penguins ; the carnivorous birds are adapted for tear- 



Flying Specialization 

 (Carinatae) 



Penguin 

 Aquatic Specialization 

 (Carinatae) 



A large extinct Ratite 



Fig. 26. Adaptive Radiations of the Birds. Archaeopteryx was a reptile- 

 like bird. Recent evolution has proceeded along two major lines, repre- 

 sented by the Hawk and Ki\vi. 



