Domain Eucaryota
   Subdomain Amoebota Doweld (2001)
     Kingdom Hydrobiota Doweld, 2001
       Subkingdom Hydrobiotina Doweld, 2001 [monotypic]
         Phylum Hydrozoa Owen, 1843
           1 Class Hydratea Doweld, 2001
           2 Class Stenoscyphatea Doweld, 2001 [monotypic]