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EVOLUTION OF ANIMALS 



Part V 



chinchillas, and guinea pigs. There are about 3000 species, more than in any 

 Other order of mammals. All of them feed chiefly on common plants and plant 

 products. They have one pair of chisellike incisor teeth in each jaw, and 

 molars but no canines. They are mainly small animals; the largest Uving rodent 

 is the South American capybara, about four feet long, a semiaquatic animal 

 that suggests an overgrown guinea pig. 



Lagomorpha — Gnawing Mammals (Fig. 37.11). These rabbits, hares and 

 pikas were formerly classified as a suborder of Rodentia. On the basis of 

 certain structures they have now been placed in a separate order. The cutting 

 teeth include 2 pairs of upper incisors and one pair of lower ones. Pikas are not 

 coneys, though sometimes called so. The true coney (Procavia) of Syria and 

 Africa, the Hyrax and others, resemble guinea pigs with hooflike nails and 

 belong to the Order Hydracoidea. 



Xenarthra (old name Edentata). Xenarthra meaning strange joints applies 

 to peculiar articulations of certain vertebrae. The order includes the tree 

 sloths, armadillos, and South American anteaters (Fig. 5.3). 



Carnivora (Figs. 37.12, 37.13). Dogs, wolves, foxes, raccoons, the Asiatic 

 pandas, weasels, minks, skunks, otters, mongooses, hyenas, cats, lynxes, lions, 

 tigers, and panthers are all carnivores. Aside from their strong upper and 

 lower canine teeth, the carnivores are not peculiarly specialized. The brain is 

 well developed. A suborder includes the marine carnivores — sea lions, seals 



Fig. 37.11. Pika (Ochotona). A little tailless rabbit, but 7 inches long and 3 

 inches at shoulder height. It lives in rock piles at high elevations in western North 

 America. Its high squeak is familiar about Lake Louise, Yosemite and other moun- 

 tain parks. (Courtesy, Seton: Lives of Game Animals. Garden City, Doubleday, 

 Doran and Co., 1929.) 



