202 



THE AGE OF MAMMALS 



hypothesis that both the Perissodactyla and Artiodactyla are natives of 



Holarctica, or the northern hemisphere. 



The great arsinoitheres played the part 

 in Ohgocene Africa which is now performed 

 by the rhinoceroses in the dark continent: 

 they were the giant mammals of the period. 

 The dominant feature of the head is a pair 

 of enormous forwardly-projecting bony 

 horn-cores over the snout, which in life 

 were sheathed with horn, sharply pointed 

 in the old bulls, and blunted or rounded in 

 the calves. A smaller pair of horns are 

 also seen to rise above the eyes. As re- 

 stored by Andrews, a moderate-sized bull 

 (Arsinoitherium zitleli) stands five feet nine 

 inches at the withers. The neck is short, 

 the limbs long, the feet short and spread- 

 ing, terminating in five short toes adapted, 

 like the crested grinders, to grazing. These 

 remarkable mammals, the affinities of which 

 are entirely unknown, were apparently con- 

 fined to Africa. 

 Remains of hyracoids are very numerous, indicating that they ran in 



herds composed either of large varieties (Megalohyrax) equaling the smaller 



Characteristic Mammals 



Creodont-carnivores 



5 genera 

 Ptolemaiids 



Relationships unknown 

 Myomorph rodents 

 Anthrocotheroid artiodactyls 



2 genera 

 Suoid artiodactyls 



2 genera 

 Hyracoids, or hyraces 

 Primitive proboscideans 



sub-aquatic and terrestrial 

 Barytheres 

 Arsinoitheres 

 Sirenians 

 Zeuglodonts 



By permission of the Century Company. 



Fig. 91. — The extinct giant coney Megalohyrax of the Lower Oligo- 

 cene of North Africa, together with its small successor, Hyrax, of recent 

 times. After a drawing by Charies R. Knight. 



tapirs in size, or of the smaller but still more abundant Saghatherium. All 

 these animals have an enlarged pair of fighting tusks, and the denti- 

 tion throughout is remarkably similar to that of the existing hyraces, or 



