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 ${eta}$-galactosidase activities. In addition, this strain grows when cultured at temperatures between 15 and $37^{circ}C$ 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 $16417^T$).