The Selenomonadales are an order of bacteria within the class Negativicutes; unlike most other members of Bacillota, they are Gram-negative.

[1] More recently, molecular markers in the form of conserved signature indels (CSIs) have been found specific for all Selenomonadales species.

[2] On the basis of these markers, the Selenomonadales are inclusive of two distinct families, and are no longer the sole order within the Negativicutes.

[2] Samples of bacterial strains within this order have been isolated from the root canals of healthy human teeth.

[3] The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[4] and National Center for Biotechnology Information (NCBI)[5] Anaeromusa Anaeroarcus Anaerosporomusa Pelorhabdus Acetonema Pelosinus Methylomusa Sporomusa Lucifera Sporolituus Thermosinus Propionispora Anaerospora Dendrosporobacter Anaerosinus Strömpl et al. 1999 Propionispira Megamonas Pectinatus Selenomonas lacticifex Schleifer et al. 1990 "Selenomastix" Selenomonas species-group 2 Mitsuokella Anaerovibrio Schwartzia Selenomonas Centipeda Selenomonas species-group 3 Veillonella Megasphaera [incl.