Tiramnia Grunt 1977

Genus Tiramnia Grunt, 1977 Type species Martinia uralica Chernyshev, 1902; original designation. Diagnosis Shells small to medium-sized, brachythyrid outlines, without plates or septa in either valve; fold and sulcus weakly or moderately developed; furrow in sulcus is very weak or absent. Surface smooth or with the weak, short ribs on anterior edge. Muscle field of ventral valve comparatively large, lanceolate; radial vascular imprints ramiform; axial mantle canal (vascula media) singular. Included Pennsylvanian species Arctic Russia, the northern Ural (Chernyshev 1902; Grunt 1977): Tiramnia uralica (Chernyshev, 1902), T. semiglobosa (Chernyshev, 1902) Permian, Cisuralian; T. tschaikensis Grunt, 1977; upper Pennsylvanian, Cape Chaika. Arctic Canada and Southeastern Alaska (Carter & Poletaev 1998): Tiramnia waltery Poletaev, 1998 and T. grunti Poletaev, 1998; Pennsylvanian. Greenland (Grunt 1977): Tiramnia greenlandica Grunt, 1977; Permian. China (Chao 1929): Tiramnia changchiacouensis Chao, 1929; Pennsylvanian. Ukraine (this paper) Tiramnia davidi sp. nov., Lower Pennsylvanian. Remarks Tiramnia Grunt, 1977 differs from Martinia M’Coy, 1844 by the presence of a ramified vascular system; Tiramnia differs from Jilinmartinia Li & Gu, 1980 by having single (connected) vascula media rather than paired vascula developed in the ventral interior of the latter. Tiramnia differs from the somewhat similar Postamartinia Wang & Yang, 1993 by having round, elongated, but not transverse shells, by the absence of low ribs on the flanks, and by a much shorter tongue of sulcus.