298 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1951 



patus occurs at Panama and ranges northward to Tepic, Mexico. 

 There are no Onychophora on Cuba. These curious wormlike animals 

 belong to a very ancient group known as fossils in the Middle Cam- 

 brian of British Columbia. 



THE FAUNA OF SOUTH AMERICA 



The fauna of South America reflects its very early connection with 

 North America, its later long isolation during which many strange 

 endemic types developed, now largely extinct, and its reunion with 

 North America in the Pliocene, permitting the introduction of North 

 American types of relatively recent origin. In the south it retains 

 many animal types, especially in the fresh-water fishes and inverte- 

 brates, that are relics of a very old connection with New Zealand and 

 Australia and are quite different from any found farther north. 



The fauna of South America has essentially the appearance of the 

 fauna of a large tropical island, the long isolation of which resulted 

 in the development from generalized stock of a large number of en- 

 demic types, merged with the fauna of a southern land mass including 

 New Zealand and Australia, with an intrusion of animal forms that 

 have arrived from North America since the Pliocene. In spite of very 

 marked affinities with Africa seen in the aquatic and amphibious ani- 

 mals especially, there is no necessity for assuming a direct union with 

 Africa at any time, though there may have been such a union. The 

 similarity to Africa is most probably due to the conservation of ancient 

 types once generally distributed which in the northern land masses 

 have been superseded by others better suited to present conditions that 

 have been prevented by certain barriers from reaching the southern 

 continents. Also it is probable that in Africa and especially South 

 America climatic and meteorological changes have been less extreme, 

 particularly in the fresh waters, than in the great land masses of the 

 north, which would favor the persistence of many ancient types. 



Perhaps the most characteristic feature of South America is the 

 canopy forest. Here animals live largely high above the ground. 

 To keep from falling from the canopy many mammals of widely 

 different kinds, as opossums, an anteater, porcupines, kinkajous, and 

 some monkeys, have developed prehensile tails, and the sloths have 

 enormous claws. There are no gliding animals, such as we see in 

 the northern and Old World forests, in Australia, and especially in 

 the Malayan region. Birds and butterflies are especially numerous 

 and varied. In the deep shade of the forests live many butterflies 

 with largely transparent wings and others with vivid colors on the 

 under side but dull above. A striking feature of the birds and but- 

 terflies is the extraordinary prevalence of brilliant and often flashing 

 colors, especially blue. Some of the numerous frogs are also brightly 

 colored. 



