EARLIEST REPTILES 



185 



origin by arid environmental conditions. The result is the 

 creation in Permian time of many externally analogous or con- 

 vergent groups of amphibians and reptiles which in external 

 appearance are difficult to distinguish. Yet as divergent from 

 the primitive salamander-like Amphibia and clearly of another 



PALEOGEOGRAPHY. EARLIEST PERMIAN ILOWER ARTINSKIAN-ROTLIEGENDE-AUTUNIAN). A GLACIAL TIME 



AFTER SCHUCHERT, APRIL. 1916 



Y MARINE DEPOSITS <v^' CONTINENTAL DEPOSITS ^5i5.hCE FIELDS f DIRECTION OF ICE FLOW 



^UNCERTAIN ICE FIELDS .-■VOLCANOES wol.nT4is 



Fig. 65. Theoretic World Environment in Earliest Permian Time. 

 A period of marked glacial conditions in the Antarctic region. Vanishing of the coal 

 floras and rise of the cycad-conifer floras, along with the rise of more modern insects 

 and the beginning of the dominance of reptiles. Modified after Schuchert, 191 6. 



type these pro-reptiles are different in the inner skeletal struc- 

 ture and in the anatomy of the skull they are exclusively 

 air-breathing, primarily terrestrial in habit rather than ter- 

 restrio-aquatic, superior in their nervous reactions and in the 

 development of all the sensory organs, and have a more 

 highly perfected cold-blooded circulatory system. Neverthe- 

 less, the most ancient solid-headed reptilian skull type (Cotylo- 

 sauria, Pareiasauria, of Texas and South Africa, respectively) 



