Proposed revision of the Famennian (Upper Devonian) standard conodont zonation

The proposed revision of the Famennian part of the Late Devonian Standard Conodont Zonation of Ziegler & Sandberg (1990) is the result of two main different kind of considerations. The first is philosophical, and consists in refusing: (1) the equivalence between biozones and time, and (2) the presumed phyletic concept on which this zonation was based. The second is practical, and deals with: (1) solving difficulties arose in the recognition of some biozones defined by Last Appearance Datum (LAD), (2) simplifying the zonation eliminating the zonal groups named after only one taxon. This revision is largely based on the zonation of Ziegler (1962) and the Late Devonian Standard Conodont Zonation of Ziegler & Sandberg (1990) using mostly the same zonal markers, therefore it is perfectly correlatable with them. Modifications have been only made when strictly necessary, as the aim of the proposal is not to destroy what was previously well done, but to improve and simplify the Standard Conodont Zonation, keeping stability over more than 50 years of conodont studies. The 22 zones constituting the revised zonation are defined by the First Appearance Datum (FAD) of species and subspecies whose stratigraphic ranges are well known, and have wide geographic distribution (Fig. 1), most of which have already been used as markers. Each zone is named after the species or subspecies whose FAD defines the lower boundary. The main changes regard the upper part of the Famennian, and take into account proposals already made by other authors, at least for regional zonation (Corradini, 2008; Kaiser et al., 2009; Hartenfels, 2011; Corradini et al., submitted). The stratigraphic distribution of most Famennian conodont taxa has been updated on data available in literature, and unpublished information of the authors. The lower boundary of the Famennian is identified as proposed by Klapper (2007), a revision of the current definition of the base of the Famennian is therefore suggested. The definition of the upper boundary (base of the Carboniferous System) is currently under discussion and study.