THE EOCENE OF EUROPE AND NORTH AMERICA 97 



tinue through the Eocene Period and reach a cUmax near the top, although 

 many branches of this archaic stock become extinct in the Lower Eocene. 

 The orders which may be provisionally placed in this archaic group are the 

 following: 



Marsupialia. 



jMultitubcrculata, Plagiaulacidse. 

 Placentalia. 



Insectivora. Insectivores not as yet positively identified in the Basal Eocene. 



Ta>niodonta. Edentates with enamel teeth. 



Creodonta. Archaic families of carnivores. 



Condylarthra. Primiti\'e light-limbed cursorial ungulates. 



Amblypoda. Archaic, typically heavy-limbed, slow-moving ungulates. 



This group is full of analogies, but is without ancestral affinities to the 

 higher placentals and marsupials. There are forms imitating in one or more 

 features the modern Tasmanian ' wolf ' (Thylacinus) , the bears, cats, hyaenas, 

 civets, and rodents of to-day, but no true members of the orders Primates, 

 Rodentia, Carnivora, Perissodactyla, Artiodactyla have been discovered. 



A remarkably interesting paheogeographic fact is the presence of many 

 similar if not actually related mammals in South America in the Upper 

 Cretaceous or Basal Eocene Notostylops Zone of Patagonia. Since other 

 members of this archaic fauna of North America are positively and widely 

 represented in the Basal Eocene of Europe, we have abundant proof of that 

 striking faunal community or widespread distribution of similar forms 

 of mammalian life in the latter part of the Age of Reptiles which has already 

 been referred to (p. 95). 



I. THE BASAL EOCENE LIFE OF EUROPE AND AMERICA 



There is little doubt that the extinction of the large terrestrial and 

 aquatic reptiles, which survived to the very close of the Cretaceous, pre- 

 pared the way for the evolution of the mammals. Nature began afresh 

 with the small, unspecialized members of the warm-blooded quadrupedal 

 Class to slowly Iniild up out of the mammal stock the great animals which 

 were again to dominate land and sea. One of the most dramatic moments 

 in the life history of the world is the extinction of the reptilian dynasties, 

 which occurretl with apparent suddenness at the close of the Cretaceous, 

 the very last chapter in the "Age of Reptiles." 



Close of the Age of Reptiles and BeginuiiKj of the Age of Mammals 



We are fortunate witnesses of these great events as they followed each 

 other at two widely distant points, namely on the northcn-n coast of France 

 and Belgium, and in the heart of the Rocky Mountain region in Wyoming 

 and northern Montana. 



