A Gram-positive and endospore-forming bacterial strain, designated S4(T), was isolated from the rhizosphere of ferns in Daejeon, Republic of Korea. This isolate is strictly aerobic, motile, and rod-like in shape, and it is positive for catalase, oxidase, esterase lipase, and beta-galactosidase activities. In addition, this strain grows when cultured at temperatures between 15 and 37 degrees C and at pH values ranging from 5.5 to 9.0. The DNA G+C content was determined to be 53.2 mol%. Strain S4(T) has meso-diaminopimelic acid in the cell-wall peptidoglycan it also contains menaquinone 7 (MK-7) as the predominant isoprenoid quinone and anteiso-C(15:0) (57.5%), iso-C(16:0) (11.3%), and C(16:0) (9.4%) as the major cellular fatty acids. Phylogenetic analysis based on alignments of the 16S rRNA gene sequence showed that S4(T) is affiliated with a cluster of strains within the genus Paenibacillaceae and is most closely related to Paenibacillus chinjuensis WN9(T), with 96.8% similarity. Based on the phylogenetic and phenotypic characteristics of strain S4(T), we believe that this isolate should be distinguished from all type species of the genus Paenibacillus and should thus represent a novel taxon within the genus Paenibacillus. We propose naming this type species Paenibacillus filicis sp. nov. for the rhizosphere isolate the type strain will be known as S4(T) (=KCTC 13693(T) =KACC 14197(T) =JCM 16417(T)).