ANCIENT ANIMALS 



431 



lower leg, and beyond this an irregular subdivision which is roughly 

 comparable to the foot skeleton of the primitive land vertebrates. 



Fig. 27.16. Modern lungfishes. Upper, the Australian lungfish, Neoceratodus (Ceratodus). 

 Center, the South American lungfish, Lepidosiren. Lower, the African lungfish, Protopterus. 

 (Courtesy Chicago Natural History Museum (upper) and American Museum of Natural 

 History.) 



The steps that led to the adoption of land life by the ancestral am- 

 phibians can only be surmised, but Romer has propounded an interesting 

 theory. He points out that many of the earliest amphibians were fairly 

 large carnivores that still spent most of their time in the water, living 

 alongside of lobe-finned fishes similar in habits and structure and differing 



