INTRODUCTION 79 



Taeniodonta Ancylopoda 



Pholidota Sirenia 



Tubulidcntata Enibrithopoda 



Lemuroidea Hyracoidea 



Amblypoda (possibly represented) Zeuglodontia 



Proboscidea 



We can most readily understand the absence of the four peculiarly African 

 orders, the Proboscidea, Sirenia, Hyracoidea, Embrithopoda. The peripty- 

 chid family of Amblypoda is possibly represented by some animals described 

 by Ameghino. The absence of many orders highly characteristic of the 

 Eocene of the northern hemisphere is more striking, namely, Artiodactyla, 

 Perissodactyla, Ancylopoda, Chiroptera, Carnivora-Fissipedia. The mam- 

 malian history of South America during the Age of Mammals is further 

 remarkable because of the extinction of the Insectivora which are appar- 

 ently represented in the small Lower Miocene genus Necrolestes, which is 

 analogous to the Ckrysoch.loris or Cape golden mole of South Africa. 



An interesting parallel with Africa in Eocene and Oligocene times is in 

 the entire absence of true Car nivora of the dog or cat families, whose func- 

 tion of preying upon the Herbivora and other mammals was exclusively 

 performed in Africa by the archaic Creodonta, and in South America by the 

 archaic carnivorous Marsupialia. This freedom from attacks of the higher 

 specialized carnivores constituted a condition especially favorable to the 

 wonderful adaptive radiation in South America of the opossums (Didel- 

 phyidae), hystricomorph rodents (cavies, tree porcupines, viscachas), as well 

 as edentates (sloths, armadillos, glyptodonts, anteaters), and of four very 

 specialized and peculiar orders of ungulate type. 



General Conclusions 



This review of the sources of the world's supply of mammals shows that 

 there were various degrees of kinship or community of life between the conti- 

 nents, as follows: (1) close kinship of the Holarctic Region, namely. North 

 America, Asia, and Europe, having the majority of the pre-Miocene orders of 

 mammals in common, and separated (;hiefly by the apparently early con- 

 tributions of Africa to Europe and of South America to North America; 

 (2) separation of the Africa- Ethiopian Region as a center of evolution of four 

 or five orders of mammals not found elsewhere, although united with Europe 

 by the presence in common of two orders of mammals and probably others 

 to be discovered; (3) South America, with the closest early kinship with 

 North America, more ancient kinship with Australia, remote kinship with 

 Europe, and still more remote kinship with Africa. These degrees of relation- 

 ship are just what we should expect from a bird's-eye view of the geography 

 of the northern and southern hemispheres respectively. 



