Middle Devonian trilobites of the Saoura Valley, Algeria: insights into their biodiversity and Moroccan affinities

摘要: Trilobites are important elements of the Devonian macrobenthos; some them were collected in Chefar el Ahmar Formation, from two sections located near Beni Abbes Saoura Valley (Ougarta Basin, Saharan Algeria). This formation is characterized by alternations claystones and limestones, it considered to be late Emsian early Frasnian age. Only lower part this has yielded trilobites so far; their presence been known for a long time. Phacopines clearly dominate trilobite assemblages, with Austerops, Barrandeops, Chotecops Phacops s.l. as main genera. Two new species described (Austerops salamandaroides sp. nov. ouarouroutensis nov.), while other taxa presented open nomenclature. Comparisons made closely allied species. These occurrences have analysed terms intra- interspecific variability biodiversity. The occurrence Struveaspis maroccanica, previously Valley, provides an Eifelian age, which also confirmed Thysanopeltis Koneprusites, ostracods Bairdiocypris devonica Bufina ?subovalis.