CREATION BY EVOLUTION 



died out 15,000 to 20,000 years ago. They had attained a 

 height of about ten feet, which is about the size of most of 

 the larger living elephants. They were, however, shorter 

 legged and more massive in build than the living elephant. 



Though the jaw was shortened, the mastodons never devel- 

 oped complex grinding teeth, but had five rather simple 

 grinders in each jaw. Apparently they remained browsers 

 to the end of their days. 



While the mastodons were developing their upper tusks 

 and losing their lower ones, there arose a group of elephants 

 which lost the upper tusks and retained the lower ones, 

 though the lower jaw had shortened so much that it could 

 no longer reach the ground. These animals were the dino- 

 theres, which arose in early Miocene time from long-jawed 

 mastodons and increased to a maximum size of but little less 

 than that of the mastodons themselves. By late Miocene 

 time they reached their height of development, only to die 

 out in early Pliocene time. In the dinotheres the lower tusks 

 were not simply retained but were enlarged and recurved. It 

 is hard to guess the use to which such tusks could be put. 

 The back teeth of the dinothere resemble those of the masto- 

 don, and probably the animal had a proboscis, similar to 

 that of the elephant, else it would have had no means of 

 reaching the ground to drink. 



In late Pliocene time, while the typical mastodons were 

 browsing on leaves and twigs, some of the group began to 

 feed on grass. As already suggested, grass carries consid- 

 erable silica in its stems and leaves, so that animals which 

 feed on it must have hard teeth. The first change taken to 

 harden the teeth was to increase the number of cross ridges 

 from three or four to six or eight, and then to increase the 

 height of each ridge. Forms that attained this stage of devel- 

 opment are known as stegodons. They were short- jawed and 



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