COMMUNITIES IN DRY, OPEN LANDS 449 



in Africa, and Callisaurus in the southwestern United States. Slender 

 and swift types of snakes are characteristic of such regions. 



Among the birds of the open country, such as the larks and many 

 gallinaceous birds, cursorial habits are much more important than 

 among the forest dwellers; at the same time unusually skillful fliers 

 are present, like swallows and sand grouse. Speed in running has under- 

 gone extreme development in the plains birds, often even at the cost of 

 flight, as among the Ratitae. Emu, rhea, and ostrich are all birds of 

 the open plains and are convergently transformed by atrophy of the 

 wings, strengthening and lengthening of the hind limbs, reduction of 

 the number of toes, lengthening of the neck, and degeneration of the 

 feathers. 15 Many carinate birds of the plains have also adopted the 

 running habit. These include the road runner of southwestern North 

 America, the secretary bird of Africa, and the desert jay, Podoces, of 

 the Asiatic plateau, and conspicuously, the bustards of the Old World 

 and the tinamous of the New. Of these, the secretary bird has only 

 recently taken up running, as is shown by the fact that the young are 

 slow in developing the habit. Many plains birds with excellent powers 

 of flight do not take to the wing until pressed. 



Mammals, especially, have contributed the principal element among 

 the cursorial types. The most outstanding runners are horses, asses, 

 and zebras. Camels and giraffes may all be numbered among the fast- 

 running animals. The greater number of antelopes, and among these 

 the swiftest types, inhabit the open country. The North American 

 prongbuck is a typical cursorial animal. Many predatory animals of 

 the open country are long-limbed and thereby adapted to fast running, 

 particularly the wolves, the Cape hunting dog (Lycaon) , and the long- 

 limbed cats such as the serval (Felis serval) , caracal {Lynx caracal) , 

 and cheetah {Acinonyx) . 



Jumping animals, with long hind legs, are also especially character- 

 istic of the open country. Four genera of kangaroos with more than 

 thirty species are found in the plains of Australia, together with a large 

 number of species of kangaroo rats and mouse-like jumping marsupials. 

 On the other hand, we have already seen that in the tropical, moist, 

 thickly forested New Guinea, a few kangaroos are adapted to living 

 in trees. Their clumsiness shows that such jumping animals are ill 

 adjusted to forest life. 16 Jumping rodents have convergently assumed 

 the bipedal form of locomotion, although they belong to quite different 

 groups, in the savanna regions of other continents. Such jumping mam- 

 mals are characterized by an enormous development of the hind limbs 

 and tail and an atrophy of the forelimbs. The African jumping hare 

 (Pedetes) among the hystricomorphs, and among the myomorphs the 



