THE TRIASSIC PERIOD 



403 



They were as small and insignificant as the moles of to-day. 

 The most distinguishing thing about them is that their teeth 

 were differentiated into incisors, canines, and molars, as in 

 mammals, while almost all reptiles have merely pointed 

 teeth much alike throughout the jaw. The derivation of 

 mammals from some of the Permian land reptiles is now the 

 most favored view. 



FIG. 422. A living Mexican cycad. (Photograph by C. J. Chamberlain.) 



Conifers and cycads make the forests. A change in the 

 plants which had been in progress during the Permian was 

 clearly defined in the early Mesozoic periods. The great 

 ferns and allied trees of the Carboniferous forests were sup- 

 planted by a higher group (gymnosperms) containing the 

 conifers and the palmlike trees called cycads (Fig. 422), 



