Cenozoic and Mesozoic Eras 



O 

 o 



CO 



^-5 



GO 



I» 



"fc. 



Eh 



CHARACTERISTICS OF THE TIMES 

 AND VARIOUS TYPES 



Civilized man, modern mammals, 

 modern birds, modern insects 



Periodic glaciation, elevation of 



continents 

 Primitive man, modern mollusks, 



extinction of great mammals 



Elevation of continents; develop- 

 ment of Pre-man, rise of mod- 

 ern insects, decline of various 

 mammals 



Maximum numbers of mammals 



Rise of higher mammals 



Vanishing of primitive mammals 



Rise of primitive mammals 



Climates quite mild ; large de- 

 posits of chalk due to forami- 

 nifera (Protozoa) ; very spe- 

 cialized reptiles followed by 

 extinction of giant reptiles; 

 birdlike reptiles, toothed birds, 

 bony fishes, rise of snakes, 

 crocodiles, turtles, extinction 

 of ammonites (Mollusca with 

 coiled, chambered shells) 



Giant reptiles (dinosaurs, ich- 

 thyosaurs, pterodactyls) ; rise 

 of birds; clams and snails 

 dominant ; bony fishes, butter- 

 flies; decline of brachiopods; 

 abundant ammonites (Mollusca 

 Avith coiled, chambered shells) 



Rise of dinosaurs, primitive mam- 

 mals, bony fishes; amphibia 

 and mollusks 



REPRESENTATIVE LIFE 



Fig. 321. — Description of the periods and epochs of the Cenozoic and Mesozoic 

 Eras of geologic time. Representatives of life during these times are shown at the 

 right. (Not drawn to scale.) (Compare with Pig. 320.) 



