Limnomedusae is an order of hydrozoans.
Taxonomy 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
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