, Western Sahara ,  Algeria  ( Ahaggar ), the southern region of Mauritania ,  Senegal , northern  Guinea , central Mali,  Burkina Faso , western  Niger  and northern  Nigeria . E. megalocephalus Cherlin, 1990 0 Cherlin's saw-scaled viper Red Sea  island between Yemen and  Eritrea  ( Dahlak Archipelago ). E. ocellatus