Chemotaxonomic parameters, phylogenetic analysis of the 16S rRNA gene, phylogenetic analysis of 90 housekeeping genes and 855 core genes, amino acid identity (AAI), average nucleotide identity (ANI) and genomic characteristics were used to examine the 13 species of the genusMeiothermuswith validly published names to reclassify this genus. The results indicate that the species of the genusMeiothermuscan be divided into three lineages on the basis of the results of the phylogenetic analysis, AAI, the guanine+cytosine (G+C) mole ratio, the ability to synthesize the red-pigmented carotenoid canthaxanthin and the colony colour, as well as other genomic characteristics. The results presented in this study circumscribe the genusMeiothermusto the speciesMeithermus ruber,Meiothermuscateniformans,Meiothermustaiwanensis,Meiothermuscerbereus,Meiothermus hypogaeus,Meiothermusluteus,MeiothermusrufusandMeiothermusgranaticius, for which it is necessary to emend the genusMeiothermus. The speciesMeiothermussilvanus, which clearly represents a separate genus level lineage was not reclassified in this study for lack of any distinctive phenotypic or genotypic characteristics. The results of this study led us to reclassify the speciesMeiothermuschliarophilus,Meiothermustimidus,MeiothermusroseusandMeiothermusterraeas species of a novel genus for which we propose the epithetCalidithermusgen. nov.