Genus Johnsoniana nom. nov.

Type species

Spirifer oceani d’Orbigny, 1849; original designation (by monotypy).

Diagnosis

Shells small to medium-sized, pentagonal or trapezoidal outline with equibiconvex profiles; ventral interarea triangular, medium high, concave only under apex, apsacline to catacline with denticulate hinge line equal to the width of shell; cardinal extremities acute but not mucronate; delthyrium narrowly elongate, triangular, high, partly covered by pseudodeltidium; shallow ventral sulcus and median depression on fold clearly limited by coarse rounded opposite plica, divided each valve into three depressed areas; flank plications absent; anterior commissure subrectilinear. Surface smooth or with concentric wrinkles and obscure irregular radial striae (10–12 per mm). In ventral valve strong deltirial ridges, boarding delthyrium, septum and dental plates absent; in dorsal valve short base of crural plate and flat ctenophoridium. Shell substance impunctate.

Stratigraphic and geographic range

Western Europe (Belgium), Russia, Urals (Bashkortostan); Mississippian, from the Late Tournaisian to Viséan (late Warnantian or late Asbian).

Included species

Type species only.