Class Proteobacteria Stackebrandt et al. 1988 nom. rej. see Phylum Proteobacteria Garrity and Holt 2001 nom. nud.
   Subclass alpha see Class Alphaproteobacteria "Garrity and Holt 2001" nom. nud.
     Group 4 see Order Sphingomonadales "Garrity and Holt 2001" nom. nud.
       Family Sphingomonadaceae Kosako et al. 2000
         1 Genus Sphingomonasᵀ Yabuuchi et al. 1990
         2 Genus Erythrobacter Shiba and Simidu 1982
         3 Genus Erythromicrobium Yurkov et al. 1994 see Genus Erythrobacter Shiba and Simidu 1982
         4 Genus Porphyrobacter Fuerst et al. 1993 see Genus Erythrobacter Shiba and Simidu 1982
         5 Genus Zymomonas Kluyver and van Niel 1936 (Approved Lists 1980)
         6 Genus Sandaracinobacter Yurkov et al. 1997 nom. inval.