Kingdom [Animalia] Linnaeus, 1758 - animals
   Subkingdom Protozoa Goldfuss, 1818 see Kingdom Protozoa Goldfuss, 1818
     Class Ciliata see [unranked] ciliates
       Order Spirotricha
         Suborder Heterotricha Stein, 1859
           Genus [Spirostomum] Ehrenberg, 1834
             Spirostomum ambiguum (Müller, 1786) Ehrenberg, [1834]