Animals Before Man 



short paddles merely aids to locomotion, but 

 in plesiosaurs the tail was short, serving mainly 

 for a rudder, and swimming effected almost en- 

 tirely by the greatly developed paddles. In 

 this group of reptiles, as with pterodactyls, the 

 life of our continent seems to have lagged some- 

 what behind that of Europe, for while they 

 abounded there during the Lias, the lower or 

 earlier part of the Jurassic, here we do not find 

 them until the Cretaceous is reached. 



Dinosaurs no longer completely dominated 

 the world of living beings as they did during 

 the Jurassic, but they still formed in North 

 America, as elsewhere, an important portion of 

 the fauna. 



The best known and presumably common- 

 est dinosaurs of the Cretaceous were the pre- 

 dentate iguanodons,^ represented here by Thes- 

 pesius and his relatives, which ranged over a 

 wide extent of territory and have been found 



* Iguana-toothed, from the resemblance of their teeth, and 

 especially the manner of their attachment, to those of a modern 

 iguana. The iguanodons of Europe are found in the Upper 

 Jurassic; still another instance of tardiness on our part, though 

 very likely due to the group having originated abroad. 



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