A thermophilic, aerobic, Gram-stain-negative, filamentous bacterium, strain PRI-4131(T), was isolated from an intertidal hot spring in Isafjardardjup, NW Iceland. The strain grew chemo-organotrophically on various carbohydrates. The temperature range for growth was 40-65 °C (optimum 55 °C), the pH range was pH 6.5-9.0 (optimum pH 7.0) and the NaCl range was 0-3 % (w/v) (optimum 0.5 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PRI-4131(T) represented a distinct lineage within the class Caldilineae of the phylum http://dx.doi.org/10.1601/nm.550Chloroflexi. The highest levels of sequence similarity, about 91 %, were with Caldilinea aerophila STL-6-O1(T) and Caldilinea tarbellica D1-25-10-4(T). Fermentative growth was not observed for strain PRI-4131(T), which, in addition to other characteristics, distinguished it from the two Caldilinea species. Owing to both phylogenetic and phenotypic differences from the described members of the class Caldilineae, we propose to accommodate strain PRI-4131(T) in a novel species in a new genus, Litorilinea aerophila gen. nov., sp. nov. The type strain of Litorilinea aerophila is PRI-4131(T) ( = DSM 25763(T) = ATCC BAA-2444(T)).