The taxon was erected by Danish marine biologist
Paul Lassenius Kramp in 1938 to accommodate certain
families of hydrozoans with
biphasic life histories. It includes
genera with
medusae with ecto-endodermal
statocysts and with
gonads alongside their radial canals, and also genera which have
polyps that are not covered by a
theca. Molecular analysis performed by Collins in 2006 has since shown that the Limnomedusae are not
monophylic. The family Armorhydridae, which contains a single genus and a single species,
Armorhydra janowiczi, is found living in coarse sediment, has hollow tentacles and has no radial canals. It seems to share few morphological features with the other families and probably belongs elsewhere. The inclusion of Microhydrulidae is also dubious. The medusa stage is not known and the tiny polyp has no tentacles nor mouth.
Systematic list The World Register of Marine Species currently lists the following families and genera: • Family
Armorhydridae Swedmark & Teissier, 1958 • Genus
Armorhydra Swedmark & Teissier, 1958 • Family
Microhydrulidae Bouillon & Deroux, 1967 • Genus
Microhydrula Valkanov, 1965 • Genus
Rhaptapagis Bouillon & Deroux, 1967 • Family
Monobrachiidae Mereschkowsky, 1877 • Genus
Monobrachium Mereschkowsky, 1877 • Family
Olindiidae Haeckel, 1879 • Genus
Aglauropsis Mueller, 1865 • Genus
Astrohydra Hashimoto, 1981 • Genus
Calpasoma Fuhrmann, 1939 • Genus
Craspedacusta Lankester, 1880 • Genus
Cubaia Mayer, 1894 • Genus
Eperetmus Bigelow, 1915 • Genus
Gonionemus A. Agassiz, 1862 • Genus
Gossea L. Agassiz, 1862 • Genus
Hexaphilia Gershwin & Zeidler, 2003 • Genus
Limnocnida Günther, 1893 • Genus
Maeotias Ostroumoff, 1896 • Genus
Nauarchus Bigelow, 1912 • Genus
Olindias Mueller, 1861 • Genus
Scolionema Kishinouye, 1910 • Genus
Vallentinia Browne, 1902 ==References==