CHAPTER VII 

 FORM EVOLUTION OF THE REPTILES AND BIRDS 



Appearance of earliest reptile-like forms, the pro-Reptilia, followed by the first 

 higher reptiles. Geologic distribution and environment of the various 

 extinct and existing orders of reptilia. Evolutionary laws exemplified in 

 the origin and development of this great group of animal life. Direct, 

 reversed, alternate, and convergent adaptation. Modes of offense and 

 defense. Terrestrial, fossorial, aquatic, and marine radiation. Aerial 

 adaptation. The Pterosaurs. First appearance of bird-like animals. 

 Theories regarding the evolution of flight in birds. Theories as to the 

 causes of arrested evolution. 



The environment of the ancestor of all the reptiles was a 

 warm, terrestrial, and semi-arid region, favorable to a sensitive 

 nervous system, alert motions, scaly armature, slender limbs, 

 a vibratile tail, and the capture of food both by sharply pointed, 

 recurved teeth and by the claws of a five-fingered hand and 

 foot. The mechanically adaptive evolution of the Reptilia 

 from such an ancestor is as marvellous and extreme as the 

 subsequent evolution of the mammals; it far exceeds in di- 

 versity the radiation of the Amphibia and extends over a pe- 

 riod estimated at from 15,000,000 to 20,000,000 years. 



The Permian Reptiles of North America and South 



Africa 



The experiments of the Amphibia in adapting themselves 

 to the Permian continents with their relatively dry surfaces 

 and seasonal water pools and lagoons are contemporaneous 

 with the first terrestrial experiments and adaptive radiations 

 of the Reptilia, a group which was particularly favored in its 



