Hemisphaerocoryphe platinflata n.sp. is described from the Lower Middle Ordovician of north-western Russia (Upper Volkhov Stage). This species expands the stratigraphical occurrence of the genus downwards into the Upper Arenig and is therefore important for phylogenetic studies. The new data support the idea that the closely related genus Krattaspis Öpik, 1937 is an ancestor of Hemisphaerocoryphe.
A new trilobite species of Hemisphaerocoryphe from the Arenig of the St. Petersburg area, Russia