Oriental region. Other interesting forms character- 

 istic of this region, although not exclusive to it, in- 

 clude two kinds of loris ; the pangolins, an elephant, a 

 tapir ; two rhinoceroses, several species of deer and 

 antelopes, wild pigs, many rodents, a porcupine :_ the 

 tiger among several other cats; bears, several kuids 

 of monkey : and, among birds, many pheasants, the 

 bee-eaters, rollers, broadbills, bulbuls, and sunbirds. 

 Many kinds of poisonous snakes occur, and lizards 

 are well represented. True frogs and toads occur; 

 tree frogs and salamanders do not. The most primi- 

 tive spadefoot toads, Pelobatidae, occur here, other 

 forms being found in Europe and North America. 

 The Apoda also occur throughout the Oriental re- 

 gion ; elsewhere, only in the Neotropical and Ethi- 

 opian regions. A varied fish fauna exists. 



There is a marked difference between the fauna 

 of northern and southern India ; probably a conse- 

 quence of the extensive volcanic eruptions that oc- 

 curred in early Tertiary which devastated extensive 

 areas in central India, the so-called Deccan traps, and 

 formed an effective East- West barrier that persists 

 even at present to some extent. Southern India and 

 Ceylon have a fauna related generically to that of 

 ,Siam, Indo-China, the Malay peninsula, the East 

 Indies, and the Philippines, the extensive Tertiary 

 intrusion of the sea between southern India and 

 Ceylon and the eastern portion of the region, has 

 permitted the extensive evolution of distinct species 

 in the areas. The various islands of the East Indies 

 that fall within this region have received their fauna 

 during the various times they were connected by dry 

 land with each other and with the mainland. 



Holarctic region 



The broad Bering land bridge connected North 

 America and Asia through much of the Tertiary, and 

 there was considerable movement of animals back 

 and forth between the two continents. There is_ simi- 

 larity at least in the genera of many animals in the 

 northern portions of the two continents, and many 

 species are found in both areas. Salamanders are 

 largely limited to the Holarctic; edentates and pri- 

 mates, other than man, are mostly lacking. The horse 

 and camel evolved first in North America and then 

 spread to Eurasia and Africa but became extinct in 

 North America. The horse was reintroduced into 

 North America within historic time by the white man. 

 As one progresses southward on the two conti- 

 nents below the Arctic tundra and coniferous forest, 

 the fauna changes (Udvardy 1958) enough to sepa- 

 rate the Palaearctic and Nearctic sub-regions. The 

 chief differences distinguishing the two are at the 

 level of species and genera and a few families. Dif- 

 ferences are more pronounced among birds and rep- 



tiles than with mammals. Antelopes, sheep, goats, 

 and certain other groups are in greater variety of 

 species in the Palaearctic ; water moles of the sub- 

 family Desmaninae are unique to the sub-region. On 

 the other hand, the Nearctic has several families of 

 birds, such as the vultures, turkeys, mockingbirds, 

 vireos, and wood warblers that have not spread into 

 Asia and Europe. Rattlesnakes, salamanders (Am- 

 bystomidae), suckers, and catfishes common to the 

 Nearctic are either absent in the Palaearctic or poorly 

 represented. 



FAUNISTIC SYSTEMS 



When populations become isolated geo- 

 graphically, they tend first to differentiate into sub- 

 species differing in superficial characteristics, then 

 into new species that would not interbreed even if 

 the isolation were lost, and finally into genera and 

 units of still higher rank. There is a general rela- 

 tion between the size of the area and the extent to 

 which taxonomic differentiation proceeds. Continen- 

 tal masses isolated from one another are usually pre- 

 requisite to the development of orders and families, 

 and the analysis of geographic distribution of animals 

 at these taxonomic levels is recognized in the realms, 

 regions, and sub-regions already discussed. Each of 

 these major geographic areas is subdivided into units 

 of lesser size, wherein genera, species, and subspecies 

 become differentiated. There has been considerable 

 study of different methods of recognizing, evaluating, 

 and classifying these lesser units in the distribution 

 of animals which has resulted in different faimisttc 

 systems. The more important of these systems need 

 now to be analyzed, especially in reference to the 

 Nearctic sub-region. 



Faunal areas 



The first attempt to subdivide North America 

 into geographic units of biological significance was 

 made by Schouw in 1823, for plants. His work stim- 

 ulated zoologists to undertake a number of similar 

 efforts (Kendeigh 1954). J. A. Allen (1892) devel- 

 oped one of the best and most realistic of thefaunistic 

 systems. The northern hemisphere was divided into 

 circumpolar arctic and north temperate realms and 

 an American tropical realm separate from tropical 

 realms in the eastern hemisphere. The north tem- 

 perate realm he divided into North American and 

 Europaeo-Asiatic regions, and into cold and warm 

 temperate sub-regions. There is considerable merit 

 in this system : in the Holarctic, a close similarity of 

 the North American and Eurasian faunas obtains in 



272 Geographic distribution of communities 



