A novel filamentous actinomycete strain, designated TRM 46004(T), was isolated from sediment of Aiding Lake in Tulufan Basin (42° 64' N 89° 26' E), north-west China. The isolate was characterized using a polyphasic approach. The isolate formed abundant aerial mycelium with few branches and vegetative mycelium, occasionally twisted and coiled; spherical sporangia containing one to several spherical spores developed at the ends of short sporangiophores on aerial mycelium. The G+C content of the DNA was 65.2 mol%. The isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and xylose, galactose and ribose as the major whole-cell sugars. The diagnostic phospholipids were phosphatidylethanolamine, phosphatidylcholine and phosphatidylglycerol. The predominant menaquinones were MK-9(H4), MK-9(H6) and MK-9(H10). The major fatty acids were iso-C16 : 0 and anteiso-C17 : 0. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain TRM 46004(T) formed a distinct lineage within the family Pseudonocardiaceae and showed 91.7-96.1 % 16S rRNA gene sequence similarity with members of the family Pseudonocardiaceae. On the basis of the evidence from this polyphasic study, a novel genus and species, Longimycelium tulufanense gen. nov., sp. nov., are proposed. The type strain of Longimycelium tulufanense is TRM 46004(T) (= CGMCC 4.5737(T) = NBRC 107726(T)).