The taxonominal status of the nomina Lesueuria Milne Edwards, 1841 and Lesueuriidae Chun, 1880, and introduction of a new genus and a new family for Lesueuria pinnata Ralph & Kaberry, 1950, as well as an additional new species of the new genus (Ctenophora, Lobata)

The nomenclatural problems posed by the nomen of the ctenophore species Lesueuria vitrea Milne Edwards, 1841, type species of the genus Lesueuria Milne Edwards, 1841 which is type genus of the family Lesueuriidae Chun, 1880, and by a few other species long referred to this genus and family, are addressed, and new solutions are proposed for some of them. For the species Lesueuria pinnata Ralph & Kaberry, 1950, an unusual ‘finned’ lobate ctenophore from the southern Pacific Ocean, a new genus and a new family are introduced. It is shown that the nomenclatural problems discussed in this paper raise difficulties for four distinct reasons, related to four different basic concepts of zoological nomenclature: those of ‘name-bearing type’ or onomatophores, of ‘type species’ of genera or nucleospecies, of availability, validity and nomen dubium, and of ‘nomenclatural stability’. The fact that specimens of this group are ‘fragile’ and difficult or impossible to fix and keep in collections requires recourse to indirect methods (detailed description, good iconography and molecular sequencing) applied to ‘ephemeral’ type specimens (holotypes or neotypes) to objectify and stabilize the nomenclature in this group.