An orange, Gram-reaction-negative and aerobic bacterium, designated MC 3718T, was isolated from a tundra soil near Ny-?lesund, Svalbard archipelago, Norway (78�X N). The cells were motile with either a polar or a subpolar flagellum and reproduced by budding or asymmetrical cell division. Growth occurred at 4-37 �XC (optimum 28-30 �XC) and at pH 6.0-10.0 (optimum pH 9.0). Many cells accumulated poly-�]-hydroxybutyrate granules and contained a single large polyphosphate granule at a pole or in the middle of the cell. Cell walls contained meso-diaminopimelic acid as the diagnostic diamino acid, and ubiquinone 10 was the main respiratory quinone. Strain MC 3718T contained summed feature 3 (comprising C16 : 1�s7c and/or C16 : 1�s6c; 29.49 %), summed feature 8 (C18 : 1�s7c and/or C18 : 1�s6c; 29.38 %), C17 : 1�s6c (10.15 %), C14 : 0 2-OH (9.05 %) and C16 : 0 (6.84 %) as the major cellular fatty acids. The main polar lipids were two sphingoglycolipids, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, three unknown phospholipids and two unknown polar lipids. Carotenoids were detected. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain MC 3718T belonged to the family Sphingomonadaceae. The DNA G+C content was 67.2 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain MC 3718T is considered to represent a novel genus and species in the family Sphingomonadaceae, for which the name Sphingoaurantiacus polygranulatus gen. nov., sp. nov. is proposed. The type strain of Sphingoaurantiacus polygranulatus is MC 3718T (= CCTCC AB 2014274T = LMG 28636T). Emended descriptions of the genera Sandarakinorhabdus, Polymorphobacter and Rhizorhabdus and the species Sandarakinorhabdus limnophila, Rhizorhabdus argentea and Sphingomonas wittichii are also provided.