152 



ZOOLOGY 



Advent of 

 warm- 

 blooded 

 animals 



Flowering 

 plants 



Mesozoic those strange reptiles known as dinosaurs 

 became prominent, and this type continued to develop, 

 producing carnivorous and herbivorous species, many 

 of them of immense size. One of the best-known dino- 

 saurs is the Diplodocus, of which a skeleton may be seen 

 in the museum at Pittsburgh. The tail and neck are 

 both very long, and the head is so small as to be incon- 

 spicuous. Many dinosaur skeletons are exhibited in 

 the American Museum in New York and in the National 

 Museum at Washington. Some were protected by mas- 

 sive bony armor plates, crests, or spines. All, however, 

 had small brains, and they must have been stupid ani- 

 mals. For millions of years they flourished, but finally 

 died out completely at the end of the Mesozoic. What 

 destroyed them, we do not know ; they may have been 

 short of food, or perhaps the mammals learned to eat 

 their eggs, which they did not know how to protect. 



9. While the dinosaurs were rulers of the earth, many 

 important events were taking place. Warm-blooded 

 creatures evolved from reptilian types, one series devel- 

 oping wings and becoming birds, the other retaining 

 the four walking legs and giving rise to the mammals. 

 The early birds, like their reptilian ancestors, were 

 toothed. Of the first mammals we know little ; but 

 they were small, and are believed to have laid eggs, 

 like the Australian duckbill of the present time. 



Another event of scarcely less importance was the 

 appearance of flowering plants, and with them of types 

 of insects adapted for visiting flowers. The latter 

 appear to have come in principally with the development 

 of herbaceous vegetation at the end of the Mesozoic and 

 during the Cenozoic. The first flowering plants were 

 woody, and were mostly, if not wholly, pollinated 

 through the agency of the wind, or at any rate without 



