The Hirnantian graptolites Normalograptus persculptus and 'Glyptograptus' bohemicus: Stratigraphical consequences of their synonymy

It is demonstrated that 'Glyptograptus' bohemicus is a junior subjective synonym of Normalograptus persculptus. The first appearance of N. persculptus appears to be diachronous, posing problems for Hirnantian biozonation. In China, N. persculptus co-occurs with N. extraordinarius. We favour here an extension downwards of the existing persculptus Biozone, the base being defined by the incoming of N. persculptus, with the lower part of the biozone designated the extraordinarius Subzone.