RODENTS OF LIBYA 59 



approach, respectively, only the southeastern and southwestern mar- 

 gins of the Sahara. The members of this distinctive family are regarded 

 by most systematists as being related to the hystricomorph rodents 

 and therefore have few relatives in Africa. Other hystricomorph genera 

 in Africa, such as Hystrix, Atherurus Cuvier, Thyronomys Fitzinger, 

 Pedetes Illiger, and Petromys A. Smith, are, except Hystrix, confined to 

 Africa south of the Sahara. That the genus Pectinator is "doubtfully 

 represented in the Pliocene of India" (Darlington, 1957, p. 392) 

 strengthens the hypothesis of a Saharo-Sindien Faunal Region. 



The fat-tailed sand rat, Pachyuromys duprasi, is apparently con- 

 fined to the Saharan steppe of Egypt, Libya, Tunisia, Mauritania, 

 and Algeria. This unique, monotypic genus is probably most closely 

 related to Meriones but unlike the latter genus has undergone an in 

 situ development in North Africa. 



The range of the sand rat, Psammomys obesus, is usually more coastal 

 than other jirdlike rodents and includes coastal northern Sudan in 

 addition to North Africa, the Isthmus of Sinai, and adjacent Israel 

 and Arabia. The genus Psammomys, although a significant element of 

 the rodent fauna of North Africa, is related to the genera Meriones 

 and Rhombomys and is probably of Asiatic origin. 



Sekeetamys calurus Thomas, the bushy-tailed jird, known only from 

 Sinai, Israel, and eastern Egypt, is probably the most localized in 

 distribution of any of the species of Saharo-Sindien rodents. This 

 species has apparently undergone a rapid in situ development in this 

 restricted area owing to its narrow ecological tolerances. 



Three monotypic genera, Rhombomys, Calomyscus, and Nesokia, are 

 confined almost exclusively to the Asian portion of the Saharo-Sindien 

 Region. Rhombomys ranges from Turkmenia and eastern Iran into 

 Chinese Turkestan and Mongolia; Calomyscus is found in the dry 

 foothill areas of Turkmenia, Iran, Afghanistan, and Baluchistan; 

 the range of Nesokia extends from India and Baluchistan to Arabia 

 and Egypt. 



In addition to the endemic and characteristic genera and species of 

 the Saharo-Sindien Region, several kinds of rodents have intruded 

 into the peripheral desert areas of Southwest Asia from Europe, the 

 high latitude steppes and deserts of Russia, and the subtropical parts 

 of the Oriental region, while some typical European and African 

 rodents have penetrated into peripheral Saharan portions of North 

 Africa. 



The squirrel Spermophilopsis Blasius; the dipodid genera Salpingotus 

 Vinogradov, Pygeretmns Gloger, Paradipus Vinogradov, Dipus Zim- 

 mermanu, and Stylodipus G. Allen; and the mole-vole Ellobius are 



