672 GEOLOGY 



Its vitality is further shown in that its descendants became a dom- 

 inant feature in the Mesozoic floras that followed. 



II. The Land Animals 



The Amphibians. The amphibians which reached their climax 

 in the later portion of the Pennsylvanian period, were still abun- 

 dant in the early Permian, but before the end of the period, they were 

 overshadowed by the rise of the reptiles, which were without doubt 

 their descendants. The Permian amphibians were much like 

 those of the preceding period, but showed some advance in organ- 

 ization, and some reptilian tendencies. The amphibians of this 

 period included the earliest known type of modern amphibians 

 (Lysorophus) , so far as now known, peculiar to the North American 

 Permian. 



Primitive reptiles. 1 While the reptiles probably began to dif- 

 ferentiate from amphibians earlier, the oldest certain relics of 

 reptiles go back but little beyond the beginning of the Permian. 

 Before the close of the period the group was large and complex. 

 At least three distinct phyla are known to have existed. One of 

 them (Pclycosaurus) , pronouncedly reptilian in character, had 

 branched off before the close of the Pennsylvanian period. Another 

 (Cotylosaurus) had a singular development of dermal carapace*, 

 strongly suggestive of turtles, and unknown outside of North 

 America. The third phylum included small, crawling reptiles, with 

 large heads, short tails, powerful and short limbs, whose nearest 

 and yet rather remote relatives (pareiasaurus) are found in South 

 Africa. The American forms were probably derived from the same 

 stock as their African allies, but the types in the two continents 

 had, as a result of long isolation, become somewhat distinct . 

 The origin of the branch of the reptiles which gave rise to the 

 mammals, was probably in Africa. 



Some of the reptiles possessed peculiar interest because of the 

 mammalian aspect of their skulls, their teeth, and some other part- 

 of their skeletons (Fig. 460). These were especially abundant 



1 Williston, The Fauiuil Relations of the Early Vertebrates, Jour. Geol., 

 Vol. XVII, 1909. 



