ENVIRONMENT OF THE TITANOTHEEES 



131 



3. Boreal forest Tiaiitat. — Characteristic of north 

 temperate zones with cold winters. The "temperate 

 rain forests" of Schimper, partly interspersed with 

 meadowlands. This zone includes the whole of primi- 

 tive northern Europe and North America south of the 

 tundra zone. In Asia it includes the whole of Siberia, 

 grading on the south into the high "steppe" and high 

 "plateau" regions and on the north into the Arctic 

 tundras or barren grounds. It is the great boreal 

 zone of North America, favored both by woodlands 

 and meadows and by sufficient rainfall. The ungulates 

 are very numerous, especially genera of Bovidae, 

 Cervidae, and Suidae. 



4. Tundras and barren ground habitat. — In this low- 

 lying, north circumpolar region trees are scarce or 

 absent, except the willows and birches of the river 

 bottoms, and the subsoil is frozen throughout the year. 

 The ungulates are now represented only by the musk 

 ox {Ovibos moschatus) and several species of reindeer 

 (Rangifer); formerly by the mammoth and the horse 

 in Alaska and Siberia during the period of greater 

 forestation. 



5. Higher plains and plateaus. — Mesas, table-lands 

 (as in Tibet and the Himalayas), and the desert 

 plateaus of the Rocky Mountains and Andes, altitude 

 3,000 to 6,000 feet or more; vegetation scattered, 

 sparsely forested, both grasses and shrubs abundant; 

 or rocky and open country with occasional forests. 

 Climate generally severe in winter. This zone grades 

 into the "high steppes" of Asia, the veldt of South 

 Africa, the high plains of North America. It is mostly 

 open country adapted to grazers with hypsodont teeth, 

 long limbs, and slender feet, or to the cursorial and 

 gregarious Herbivora. 



6. High steppe and desert habitat. — Treeless and arid 

 wastes, steppes, and deserts of central Asia (such as 

 the Desert of Gobi) or of Persia and Asia Minor, 

 reaching an altitude of 6,000 feet, usually not so rich 

 in flora and fauna as the high plateau. Climate 

 extremely severe in winter. Inhabited chiefly by 

 grazers. In Asia, among the Equidae we find the 

 kiang {Eguus Jciang) of Tibet, the dziggetai {E. 

 hemionus) of Mongolia, the wild horse {E. przewalslcii) 

 of the Desert of Gobi or the Kobdo district of western 

 Mongolia. The kiang of Tibet and Turkestan prefers 

 desert places near lakes and rivers, seeking coarse, wiry 

 pasture and rough, hard grasses. The dziggetai ranges 

 from the lowland steppes of Turkestan to the high 

 plateaus (1,680 meters) of the deserts of Mongolia. 

 In this zone among the Artiodactyla we find the wild 

 Bactrian camel {Camelus bactrianus), the saiga ante- 

 lope {Saiga tartarica), and the Persian gazelle {Gazella 

 gutturosa). 



7. Low desert habitats. — Steppes and sandy deserts 

 of northern Africa, Syria, Arabia, Mesopotamia, and 

 the northern borders of the Arabian Sea; rocky 

 countries covered with sparsely vegetated areas and 

 thin forests, scattered shrubs, and thorny bushes. 

 Except in temperature and altitude this zone is like 

 that of the high steppes; its vegetation is sought 

 mostly by cursorial browsers and grazers with colora- 

 tion of the desert; in Africa Gazella dorcas, Addax, 

 Oryx leucoryx, and among the Equidae the north 

 African wild ass {Equus asin'us), the Somaliland ass 

 {Equus somaliensis) , the Assyrian E. hemippus, and 

 the onager {E. onager), which grazes in the low deserts 

 of Kutch and Rajputana. Neither the rhinoceroses 

 nor the tapirs have ever had representatives in these 

 low-lying desert belts. 



8. Plains habitat. — Great plains and larger river 

 valleys; broad, grassy meadows bordering glades 

 partly forested or not forested at all, extending from 

 sea level to an altitude of 6,000 feet in northern 

 latitudes. The tropical grasslands or savannas of 

 Africa, the llanos of the Orinoco, the campos of 

 Brazil, the semiarid karoos and veldts of South Africa 

 are partly included in this zone, although they also 

 approach the high steppe habitat. This zone is 

 generally adapted to grazing, hypsodont types, mostly 

 long-headed and cursorial. It is the natural habitat 

 on the Great Plains of North America of the buffalo 

 (Bison bison), of the pronghorn antelope (Antilocapra 

 americana), and formerly of the wapiti (Cervus 

 canadensis). Similarly on the plains of equatorial 

 Africa are found numerous species of antelope (mostly 

 grazers), oxen (grazers), giraffes (tfue browsers), the 

 black rhinoceros, R. (Opsiceros) bicornis (browsers and 

 grazers), and all species of zebra. The ungulates in 

 this open country are either cursorial or graviportal 

 and are well defended by horns. The Tapiridae 

 have never been adapted to a country of this kind. 

 The giraffes frequent the savanna and the thorn- 

 forested country (xerophilous woodland of Schimper). 



9. Lower river valleys habitat. — Alluvial bottom 

 lands, delta and flood-plain deposits, swamps and 

 jungles, forested or grassy lowlands near rivers or sea 

 level, typically the home of browsers rather than 

 grazers, with feet and limbs adapted to soft soil, 



j limbs both of mediportal and graviportal type, with 

 some cursorial types (such as situtungas) having 

 spreading feet. The Artiodactyla include many 

 bovines, some antelopes (such as situtungas), chevro- 

 tains, suillines, the Liberian hippopotamus {Choer- 

 opsis liberiensis) , and the primitive traguline (Dorca- 

 therium) of West Africa. Among the Asiatic rhino- 

 ceroses R. sondaicus, a browsing, brachyodont type, 



