RODENTS OF LIBYA 45 



Thus, continents having broad continental shelves were increased 

 or decreased considerably in area. The magnitude of this fluctuation 

 of sea level has been estimated to have reached 100-120 meters 

 during the height of glaciation (Darlington, 1957; after Kuenen, 

 1950). 



Even today, there are abundant indications of Pleistocene glacia- 

 tion. The higher peaks of the Caucasus and Elburz Mountains near 

 the Caspian Sea in Southwest Asia contain glacial remnants. Portions 

 of the Alps of central Europe are still enveloped in ice, and the Pyrenees 

 of northern Spain have small glaciers. East Africa has residual glaciers 

 on Mount Kenya, Mount Kilimanjaro, and on the Ruwenzori Range, 

 all of which are almost astride the equator. 



In response to these marked changes in temperatures during the 

 Pleistocene, marked changes took place in the underlying patterns of 

 floral and faunal distributions. In the Northern Hemisphere, the 

 unglaciated areas south of the "ice front" were profoundly affected 

 by periodic changes in Pleistocene climate. Widespread migrations of 

 plants and annuals occurred as a result of the gradual shifting of 

 climatic zones along the glacial front. During the moist pluvial 

 periods forest dwelling animals dispersed southward, while during the 

 dry interpluvial periods animals typical of the steppe and desert 

 regions migrated northward. Throughout the Pleistocene, there was a 

 north-south shifting of the flora and fauna in concert with the four 

 successive advances and withdrawals of the ice sheets. 



During the pluvial periods, with increased rainfall throughout 

 the world, forests and prairies expanded, and during interglacial 

 periods steppes and deserts increased in area. Some of this repatterning 

 of floral and faunal elements resulted in development of geographic 

 discontinuity owing to complex advance, retreat, readvance, and 

 interspersion of migrating populations. 



Pleistocene climatic changes affected especially the Mediterranean 

 region of North Africa. The Saharan and central portions were also 

 profoundly affected. Evidence is widespread in North Africa and the 

 Sahara to support climatic fluctuations during the Pleistocene. 



According to Flint (1947; after Brooks, 1932), in the Saharan region 

 of North Africa, two moist stages, interpreted on the basis of fossil 

 mammals, are separated by a period of aridity indicated by an accumu- 

 lation of gypsum in the soil. The numerous dry watercourses (wadis) 

 in the Sahara suggest that permanent streams were present during 

 a pluvial stage when the amount of rainfall was greater than it is 

 today. 



The occurrence in northern Africa of fossil mammals characteristic 

 of markedly different climatic zones supports other evidences that 



