Valenzuela-Ríos, 7.1. 1994 10 15 The Lower Devonian conodont Pedavis pesavis and the pesavis Zone.
Records from Europe and Western North America suggest that a diversification of Pedavis faunas took place around the base of what has been called the pesavis Zone. This level is reviewed in comparison to sequences in Western North America and Spain. Hitherto, two different taxa, Pedavis pesavis S.S. and Pedavis striatus (=Icriodus pesavis of Klapper 1969) have been used indiscriminately in defining the base of the pesavis Zone. This revision points out that the chronostratigraphic problems derived from an unknown phylogenetic history of both P. striatus and P. pesavis remain still unsolved, and thii fact challenges the continued use of either taxon as a zonal index for dating and correlating purposes. To improve this situation a new biostratigraphic unit above the delta Zone is proposed, the pandora beta - gilberti unit. This unit is unambiguosly defined, and thus it now enables accurate correlation on a global-scale basis above the delta Zone. Conodonts, biostratigraphy, Lower Devonian, Pyrenees, Nevada.