2l8 



THE ORIGIN AND EVOLUTION OF LIFE 



the widely heralded Giganiosaurus (= Brachiosaurus) , de- 

 scribed as the largest land-Hving vertebrate ever found, is 



Fig. 



gO. -\uKTii Ami.ru'a i.\ Lu.w.u Lrktaceous (Comanchian) Time. 



This period, also known as the Trinity-Morrison time, is marked by the maximum develop- 

 ment of the giant herbivorous dinosaurs, the Sauropoda. The Sierra Nevada and coast 

 ranges are elevated, also the mountain ranges of the Great Basin which give rise east- 

 ward to the flood-plain deposits (Morrison) in which the remains of the Sauropoda are 

 entombed. This epoch is prior to the birth of the Rocky IMountains, which arose be- 

 tween Cretaceous and Eocene time. Detail from the globe model in the American 

 Museum by Chester A. Reeds and George Robertson, after Schuchert. 



structurally closely related to and does not exceed in size the 

 sauropods discovered in the Black Hills of South Dakota. 

 Their size is indeed titanic, the length being loo feet, while the 



