ADAPTIVE RADIATION OF REPTILES 



193 



higher stages of perfection than the mammals. Nor does increas- 

 ing intelligence, as we shall see, favor mechanical perfection. 



Turning our survey to the origin and adaptive radiation of 

 the reptiles as a whole, we find that in Permian time all of the 



ORIGIN AND ADAPTIVE RADIATION OF THE REPTILES v». k. c«ecci«y, 1 



Fig. 72. Adaptive Radiation of the Reptilia. 



The reptiles first appear in Upper Carboniferous and Lower Permian time and radiate into 

 eighteen different orders, three of which — the Cotylosaurs, Anomodonts, and Pely- 

 cosaurs — attain their full evolution in Permian and Triassic time and later become 

 extinct. Six orders — the Ichthyosaurs, Plesiosaurs, Dinosaurs, Phytosaurs, Pterosaurs, 

 and Turtles — are first discovered in Triassic time, while five of the orders — the Ich- 

 thyosaurs, Plesiosaurs, jMosasaurs, Dinosaurs, and Pterosaurs — dominate the Cretace- 

 ous Period and become suddenly extinct at its close, leaving the five surviving modern 

 orders — Testudinata (turtles, tortoises), Rhyncocephalia (tuateras), Lacertilia (lizards), 

 Ophidia (snakes), and Crocodilia (crocodiles). These great reptilian dynasties seem 

 to have extended over the estimated ten million years of the Mesozoic Era, namely, the 

 Triassic, Jurassic, and Upper Cretaceous Epochs. Prepared for the author by W. K. 

 Gregory. 



ten early adaptive branches of the reptilian stem had radiated 

 and become established as prototypes and ancestors of the 

 great Mesozoic Reptilia. Five divisions, namely, the coty- 

 losaurs, anomodonts, pelycosaurs, proganosaurs, and phyto- 

 saurs, were destined to become extinct in Permian or Triassic 

 time, in each instance as the penalty of excessive and prema- 



