FOSSIL ANIMALS 



281 



Eras or 

 Periods. 



Cenozoic. 



Era of 

 Mammals. 



Ages or Systems. 



Quaternary or Pleis- 

 tocene (age of man and 

 recent mammals) . . 

 Tertiary: Pliocene, 

 Miocene, Eocene 



Animals Especially Charac- 

 teristic of the Era or Age. 



Man; mammals, mostly of spe- 

 cies still living. 



Mammals abundant; belonging 

 to numerous extinct families 

 and orders. 



Mesozoic. 



Era of 

 Reptiles. 



Paleozoic. 



Era of 

 Inverte- 

 brates. 



Archean. 



Cretaceous 



Jurassic. 



Triassic 



Carboniferous (age of 

 amphibians) 



Devonian (age of 

 fishes) 



Silurian (age of in- 

 vertebrates) 



Ordovician or Lower 

 Silurian 



Cambrian 



Algonkian. 

 tian. 



Lauren- 



Birdlike reptiles; flying reptiles; 



toothed birds; first snakes; 



bony fishes abound; sharks 



again numerous. 

 First birds; giant reptiles; am- 

 monites; clams and snails 



abundant. 

 First mammals (a marsupial) ; 



sharks reduced to few forms; 



bony fishes appear. 



Earliest of true reptiles. Amphi- 

 bians; lung fishes; fringe fins; 

 first crayfishes; insects abun- 

 dant; spiders; fresh-water 

 mussels. 



First amphibians (froglike ani- 

 mals); sharks; ostracophores; 

 first land shells (snails) ; mol- 

 luscs abundant; first crabs. 

 First truly terrestrial or air- 

 breathing animals; first in- 

 sects; corals abundant; mailed 

 fishes. 



First known fishes, ostracophores, 

 mailed and with cartilaginous 

 skeleton; brachiopods; trilo- 

 bites, molluscs, etc. 



Invertebrates only. 



Simple marine invertebrates. 



