REPTILIA 



215 



c. Parapsida; represented to-day by the lizards and snakes, and 



by the extinct mososaurs, ichthyosaurs, etc. 



d. Anapsida; represented to-day by the turtles, and by the extinct 



cotylosaurs and the extinct semi-chelonian, Eunotosaunis. 

 Thus we see that the reptiles had undergone an extensive adaptive 

 radiation even in the Palaeozoic. Of the several adaptive types of 



D 



Fig. 123. — Group of Palaeozoic Reptilia. A, Varanops; B, Labidosaurus; 

 C, Seymouria; D, Dimetrodon; E, Cynognathus (a mammal-like reptile) ; F, head 

 of Scymnognathus (a South- African "dog-toothed" reptile). (Redrawn from 

 Osbom, after Williston and after Gregory.) 



that period perhaps the most significant is that exemplified by the 

 lizard-like reptile Varanops (Fig. 123, A), a creature so generalized 

 that it might well be selected as an- archetypal reptile. The fact that 

 it has a skull and skeleton much like that of jnodern lizards has led 

 Williston to the conclusion that some of our modem lizards are more 



