A revision of the genus <i>Halosaccion</i> (Palmariaceae, Rhodophyta) from the Russian Pacific coast with description of the genus <i>Nothohalosaccion</i> gen. nov.

This study evaluates the diversity and distribution of species of the genus <i>Halosaccion</i> along the Russian Pacific coast using morphological data and molecular analyses. <i>Halosaccion minjaii</i> was found to be genetically distant from other species in the genus; this and its unique morphological features – namely the development of tetrasporangia in elevated sori between long sterile filaments (which are much longer than tetrasporangia) and the mode of spermatangia formation – led to the proposal of a new genus, <i>Nothohalosaccion</i>, with a single species <i>N. minjaii</i>. Data on species distribution in the north-western Pacific were refined. <i>Halosaccion americanum</i> was recorded for the first time in the Okhotsk Sea. This extended the species range north-westward. In contrast, the distribution of <i>Halosaccion microsporum</i> was restricted to northern and western parts of the Okhotsk Sea, the eastern Kamchatka coast and western Bering Sea. The distribution patterns of species of the genera <i>Halosaccion</i> and <i>Nothohalosaccion</i> are discussed in relation to the oceanography of the region. Types of the names <i>H. microsporum, Dumontia hydrophora</i> (≡ <i>Halosaccion hydrophorum</i>) and <i>Ulva glandiformis</i> (≡ <i>Halosaccion glandiforme</i>) are designated to guarantee their unambiguous use and to stabilize the nomenclature. A new genus <i>Nothohalosaccion</i> for <i>Halosaccion minjaii</i>.First record of <i>Halosaccion americanum</i> in the Okhotsk Sea.Typification of specific names in the genus <i>Halosaccion.</i> A new genus <i>Nothohalosaccion</i> for <i>Halosaccion minjaii</i>. First record of <i>Halosaccion americanum</i> in the Okhotsk Sea. Typification of specific names in the genus <i>Halosaccion.</i>