Rivers such as the Irharhar in Algeria, Libya and Tunisia and the Sahabi and Kufra rivers in Libya were active during this time although there is some doubt that they had perennial flow; they appear to have been more important in earlier humid periods. Small watersheds, wadis and rivers discharging into endorheic basins such as Wadi Tanezzuft also carried water during the AHP. In the Air, Hoggar and Tibesti Mountains, the so-called Middle Terrace was emplaced at this time. The rivers of the Sahara, lakes and their watersheds may have acted as pathways for the spread of humans and animals; the rivers were often connected to each other by alluvial fans. Proposed examples of animals that spread through rivers are the Nile crocodile and the fish Clarias gariepinus and Tilapia zillii. It is possible that the name Tassili n'Ajjer, which means plateau of the rivers in Berber, is a reference to past river flows.