Late Devonian (Famennian) phacopid trilobites from western Xinjiang, Northwest China

An early Famennian trilobite fauna represented by phacopids is recorded and illustrated from the lower member of the Hongguleleng Formation (crepida conodont Zone) near the Bulongguoer Reservoir in northwestern Xinjiang, northwestern China. In this area, the Hongguleleng Formation is rich in diverse faunas and exposes bioclastic argillaceous limestones and marls, intercalated with green calcareous shales of Famennian shallow marine shelf deposits formed in a volcanic arc-related setting. The studied material is most often incomplete, often poorly preserved as internal molds. Due to insufficient preservation of well-preserved cephala, additional material is required. However, among faunas, the Hongguleleng Formation contains specimens of Clarksonops junggariensis gen. nov. sp. nov., a so-far endemic taxon, which is the first known and described representatives of trilobites from lower Famennian deposits of northwestern China; and ?Houseops cf. olonbulagensis, a taxon encountered in western Mongolia. Their affinities with known other sighted species of the same age are discussed.