Grimmia andreaeopsis C. Muell., a species described from sterile material from the Chukotka Peninsula, is redescribed and illustrated The species is actually a member of the genus Schistidium. It can be distinguished from its closest relatives, viz. species of S. strictum complex, by the possession of a unique combination of characters: (1) inky black coloration of gametophytes; (2) strongly and asymmetrically keeled, rapidly wide-spreading to squarrose when moist, leaves; (3) cells entirely smooth, very incrassate and strongly nodulose nearly to the base of the lamina: (4) a costa totally smooth or only occasionally slightly roughened on the back below the apex, but never scabrous with conical papillae; (5) leaf margins always entire; (6) peristome teeth bluntly acuminate. Unlike most rupestral species of Schistidium it grows in wet arctic fens. S. holmenianum Steere & Brassard, a species known to be widely distributed in the Nearctic, and Racomitrium depressum Lesq. var. nigricans Kindb., a variety described from Labrador and Hudson Bay. are synonymous with S. andreaeopsis (C. Muell.) Laz. A comparison of S andreaeopsis with the Andean-Subantarctic S. anqustifolium (Mitt.) Herz is made and these species are considered to be closely related, but not conspecific, bipolar counterparts. Also, a comparison with the South Georgian S. urnulaceum (C. Muell.) Bell and the Holarctic species of S. strictum complex, which are characterized by having similar leaf cell patterns, is made. S. andreaeopsis has a circumpolar distribution, mainly within the High Arctic. In addition to the Nearctic, the species is known to occur in Svalbard, North Land, Taymyr Peninsula, Yakutia, Wrangel Island, and on the Chukotka Peninsula.
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