On a new Antarctic species of Symplectoscyphus Marktanner-Turneretscher, 1890 (Cnidaria, Hydrozoa, Sertulariidae), with an annotated checklist of the Antarctic species of the genus

A new Antarctic species of the genus Symplectoscyphus Marktanner-Turneretscher is described and figured, and its position amongst the allied Antarctic species of the genus is discussed. The material was collected from the Ross Sea area (Antarctica) during the BioRoss survey to the western Ross Sea and Balleny Islands in 2004. Symplectoscyphus frondosus, sp. nov., is unique amongst the Antarctic known species of the genus in having large, erect, rigid, muchbranched, bottlebrush-shaped stems. An annotated checklist of the Antarctic species of the genus is also included. Sixteen of the 19 known Antarctic species are endemic to the Antarctic Region (84%), two are also present in subAntarctic waters and only one has a wider distribution.