404 



ELEMENTS OF BIOLOGY 



tilian characters not found in modern birds. The tail was long and 

 the vertebrae were not fused together to form the long sacrum of 

 the modern bird. Not only did Archseopteryx have teeth, but the 

 teeth were reptilian-like. Here, then, is a form that constitutes a 

 link between these two groups of modern vertebrates. Obviously. 



FLYING REPTILE 



BIRD 



Fig. 223. — The wing bones of a pterodactyl (extinct flying reptile) and the wing 

 bones of a modern bird. (After Lucas: Animals before Man in North America, pub- 

 lished by D. Appleton and Company.) 



our present-day birds are not derived from modern reptiles, but 

 from reptilian-like ancestors at a time far back in the history of life 

 on the earth. 



Ancestry of Man. A somewhat similar path of origin of the 

 human race has been traced. After the close of the Mesozoic Era, 

 well into the Tertiary Era, appear fossils of animals resembling the 

 anthropoid apes. In the next period, the Pliocene, a variety of pri- 



