THE REPTILES AND THE BIRDS 12Q 



class was spared, for even the fresh-water and marine 

 fishes suffered decimation, while among the ammonites 

 and belemnites, and the reef -forming clams of the ocean 

 floor, not a family survived to see the dawn of the Ceno- 

 zoic era. 



There is little about the end of the Mesozoic to ex- 

 plain this world-wide destruction of many orders and 

 innumerable species of animals. The coal beds of New 

 Mexico, Colorado, Utah, Wyoming, and Montana were 

 laid down in the Upper Cretaceous (at the end of the 

 Mesozoic) and on into the Eocene (at the beginning of 

 the Cenozoic) without a marked hiatus; the oil beds of 

 eastern Texas are of Upper Cretaceous origin and, late 

 in this period, figs, breadfruits, cinnamons, laurel, and 

 tree ferns were growing in Greenland, while cycads, 

 palms, and figs were growing in Alaska. There was cer- 

 tainly no great icecap in the Northern Hemisphere at 

 the close of the Mesozoic, and only local glaciation of 

 elevated areas occurred in the Eocene. In short, there 

 was no such catastrophic change in climate as marked 

 the Permian 'stricture,' when frigidity spread over so 

 much of the world to blank out a large fraction of Paleo- 

 zoic life. The 'time of the great dying' does, in fact, coin- 

 cide with another shudder of the earth— the Laramide 

 revolution— and a warping of the continents which again 

 brought in its wake withdrawal of the seas, a drop in 

 temperature, even if moderate, and contraction of the 

 swampy lowlands with a marked change in vegetation 

 all over the world; but the dramatic thing is that 

 these rather undramatic changes, when added together, 

 should have spelled death to so many Mesozoic forms. 



It is futile to say that the great reptiles failed in the 

 evolutionary sense, because too many other animals 

 failed with them in this mysterious crisis. On the con- 

 trary, the reptiles did not fail, because they established 

 themselves as the first complete masters of the land. 

 Many of the Permian and later forms give the appear- 

 ance of being amphibious and water-bound, but in view 



