THE PHYLA HEMICHORDATA AND CHORDATA 



Fig. 18.13. Ancient amphibians. A, 

 mounted fossil skeleton, and fl, modeled 

 restoration, of Eryops, a large amphibian 

 of the Permian period. C, reconstruction 

 of a somewhat later and more advanced 

 tvpe of amphibian, Diplovertehrorj. (All 

 photographs courtesy American Museum 

 of Natural History.) 



Devonian of Greenland; these are the earhest traces of terrestrial vertebrates. 

 This confirms the behef that the well -developed forms of the Carboniferous 

 deposits (Fig. 18.13) were preceded by earlier amphibians in the Devonian or 

 Silurian. The evolution of these early amphibians must have involved a long 

 period of transition, during which fins became limbs and air breathing became 

 an increasingly important mechanism of respiration. Clearly, the first ter- 



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