MATTHEW, CLIMATE AND EVOLUTION 



257 



nating in the highly specialized Dinocerata. In South America, they 

 apparently develop during the Tertiary in absence of Artiodactyla and 

 Perissodactyla into a great variety of hoofed mammals, the Toxodontia 

 and Typotheria, Litopterna, Astrapotheria, Pyrotheria. The Arsinoi- 

 theria of the Oligocene of Africa, perhaps also the Hyracoidea and Proho- 

 scidea, may also be regarded as evolved from primitive Condylarthra, in 

 absence of the higher ungulates of the Asiatic center of dispersal. We 

 have therefore direct or inferential evidence that at the beginning of the 

 Eocene the Condylarthra inliabited the Palsearctic, Nearctic, Neotropical 

 and Ethiopian regions. There is no reason to suppose that they were 



Fig. 28. — Relationship of the Condylarthra to the Notoungulate and Subungulate groups 



of hoofed mammals 



In indicating the distribution, Egypt, Syria etc. have been included with Ethiopia, as 

 the essential facts in this case could thus best be represented. "Bunotheria" are the 

 common ancestral stock (hypothetical) of the Creodonta-Carnivora-Condylarthra-Ambly- 

 poda group. 



absent from the Oriental region, but they evidently did not reach Aus- 

 tralia or Madagascar. 



The worldwide dispersal of the condylarths at the opening of the Ter- 

 tiary (partly hypothetical and exclusive of Australasia and Madagascar) 

 may be regarded as due to the epoch of elevation and disturbance which 

 closed the Cretaceous. The subsequent development of peculiar and 

 highly specialized ungulates during the Eocene in the several great con- 

 tinents is attributable partly to the isolation of these continents during 

 that period due to submergence of the low lying connecting regions. 



