The genus
Selenomonas constitutes a group of motile crescent-shaped bacteria within the
Veillonellaceae family 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.