The taxon was erected by Danish marine biologist Paul Lassenius Kramp in 1938 to accommodate certain families of hydrozoans with biphasic life histories.

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.

The medusa stage is not known and the tiny polyp has no tentacles nor mouth.

[citation needed] The World Register of Marine Species currently lists the following families and genera:[1]