Abstract: In Naerdeman mountain, Ertai area, eastern Junggar basin, Xinjiang, Late Devonian Ammonoids Kosmoclymenia cf. tabulata Sun et Shen has been discovered in a marine volcanic and terrigenous clastic formation for the first time. This fossil is the iconic fossil for the top of Late Devonian Famennian. It provides an important paleontological basis for regional stratigraphic correlation of the Upper Devonian Kaixiweng formation.