selenomonad selenomonad members of the genus selenomonas (motile crescent-shaped bacteria in general) are referred to trivially as selenomonads. the genus selenomonas constitutes a group of motile crescent-shaped bacteria and includes species living in the gastrointestinal tracts of animals, in particular the ruminants. a number of smaller forms discovered with the light microscope are now in culture but many, especially the large selenomonads are not, owing to their fastidious and incompletely known growth requirements. selenomonad scientific classification domain: bacteria phylum: bacillota class: negativicutes order: selenomonadales family: selenomonadaceae genus: selenomonasvon prowazek 1913 type species selenomonas sputigena(flügge 1886) boskamp 1922 species see text gram stain