After “Wikispecies”

<==o Hydrozoa Owen, 1843 (polyyppieläimet)
   |?- †Spongiomorphida
   |==o Hydroida after Parker, 1982 [paraphyletic]
   |  |?- Capitata Kühn, 1913 [Hydroida: Anthomedusae in partim & Limnomedusae in partim] [not recognized by Parker, 1982]
   |  |?- Conica [Hydroida: Leptomedusae in partim & Anthomedusae in partim] [not recognized by Parker, 1982]
   |  |?- Filifera [Hydroida: Anthomedusae in partim] [not recognized by Parker, 1982]
   |  |?-o Limnopolypae [Hydroida: Limnomedusae in partim] [not recognized by Parker, 1982]
   |  |  |--o Microhydrulidae
   |  |  |  |-- Microhydrula
   |  |  |  `-- Rhaptapagis
   |  |  |--o Olindiasidae
   |  |  |  |-- Craspedacusta
   |  |  |  |-- Gonionemus
   |  |  |  |-- Gossea
   |  |  |  |-- Maeotias
   |  |  |  |-- Monobrachium
   |  |  |  `--o Olindias Müller, 1861
   |  |  |     |-- O. formosa (Goto, 1903) [Olindioides formosa Goto, 1903]
   |  |  |     |-- O. malayensis
   |  |  |     |-- O. muelleri
   |  |  |     |-- O. phosphorica
   |  |  |     |-- O. sambaquiensis
   |  |  |     |-- O. singularis
   |  |  |     `-- O. tenuis
   |  |  `--o Proboscidactylidae
   |  |     |-- Fabienna
   |  |     `-- Proboscidactyla
   |  `?-o Proboscoida [Hydroida: Leptomedusae in partim] [not recognized by Parker, 1982]
   |     |--o Bonneviellidae
   |     |  `-- Bonneviella grandis
   |     `--o Campanulariidae
   |        |-- Campanularia
   |        |-- Clytia
   |        |-- Gonothyraea
   |        |-- Hartlaubella
   |        |-- Laomedea
   |        |-- Obelia
   |        |-- Orthopyxis
   |        |-- Phialidium
   |        |-- Rhizocaulus
   |        `-- Tulpa
   |-- Hydrocorallia
   |-- Trachylina
   |-- Siphonophora
   `--o Actinulida
      |--o Halammohydridae
      |  `--o Halammohydra
      |     |-- H. adherens
      |     |-- H. coronata
      |     |-- H. intermedia
      |     |-- H. neglecta
      |     |-- H. octopodides
      |     |-- H. schulzei
      |     `-- H. vermiformis
      `--o Otohydridae
         `--o Otohydra
            |-- O. tremulans
            `-- O. vagans

After Parker, 1982

<==o Hydrozoa
   |-- Chondrophora (uimapolyypit)
   |--o Hydroida
   |  |-- Anthomedusae
   |  |-- Leptomedusae
   |  `-- Limnomedusae
   |--o Hydrocorallia
   |  |-- Milleporina (fire corals; tulikorallit)
   |  `-- Stylasterina
   |--o Trachylina
   |  |-- Laingiomedusae
   |  |-- Narcomedusae
   |  `-- Trachymedusae
   |-- Siphonophora
   `-- Actinulida

Reference(s):