PROBLEM 2, IV e Leam of Prehistoric Living Things jrom Fossils 



Fig. 490 Using our knowledge of fossils, a?i artist painted this scene of an early 

 period in the age of mammals. Which reptile do you recognize? How does the vege- 

 tation differ from that of earlier eras? (royal Ontario museum, Toronto) 



Fig. 491 Western Nebraska during the age of maimnals. In those days, according to 

 the fossils that have been found, horses roamed the plains. Later they died out. What 

 other animals can you recognize? (American museum of natural history) 



to another. But during most of this time 

 it seems likely that there was no land con- 

 nection between North and South Amer- 

 ica. The two continents were again con- 

 nected by land toward the end of this era. 

 The Age of Man. About a million years 

 ago the seventh era (Psychozoic — psy- 



ko-zo'ik) began. Manlike creatures ap- 

 peared. You will read of them in the last 

 Problem of this Unit. Meanwhile, the 

 earth was undergoing great changes in 

 climate. It was alternately cold and warm. 

 During the colder periods glaciers 

 formed on the mountain sides; thick 



