436 New York State Museum 



Life of the Mesozoic 



The Mesozoic is known as the Age of Reptiles and 

 Medieval Floras. The first mammals appeared in the 

 early Mesozoic and in the later Mesozoic the first birds 

 and true bony fishes (teleosts). Invertebrate life took 

 on a more modern aspect. The Foraminifera reached a 

 great development and were important as rock builders 

 (chalk), especially in the Cretaceous and later in the Ter- 

 tiary. Modern types of corals became established and 

 formed extensive reefs in the Jurassic. New types of 

 echinoderms replaced the old. Crinoids were abundant 

 but not diversified in the Jurassic, and certain types of 

 echinoids were abundant in the latter part of the era, 

 but starfishes were not conspicuous. Brachiopods became 

 unimportant. Most of the species belong to genera living 

 today and almost exclusively to three families. There 

 was a rapid development of pelecypods, which increased 

 in numbers and variety as brachiopods decreased. Gas- 

 tropods were less simple than Paleozoic forms and many 

 modern types had appeared by the end of the era. Among 

 the cephalopods the ammonites had a marvellous develop- 

 ment in the Jurassic, and unusual forms appeared with 

 the decline of the race toward the end of the era. Crus- 

 taceans and insects also are of a very modern appearance. 

 All groups of insects except those dependent upon flower- 

 ing plants for food are represented. 



The types of plants now dominant were introduced dur- 

 ing the Mesozoic era. Angiosperms or flowering plants 

 appeared in the Lower Cretaceous. Horsetails that re- 

 placed the Carboniferous calamites were very much like 

 those of today. Cycads were characteristic of the Trias- 

 sic and Jurassic ; ferns were common throughout the era ; 



