Conodont Stratigraphy of the European Devonian

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Abstract
Lower Devonian conodont stratigraphy is incomplete although several authors have recently contributed to its refinement. The Icriodus woschmidti woschmidti- and I. w. postwoschmidti-Faunas are Lower Gedinnian. Descendants of I. woschmidti are recorded from the higher Lower Gedinnian, which also yields some representatives of the Bischoff-Sannemann fauna. However, the latter, containing forms indicating upper Lower Gedinnian, Upper Gedinnian, and portions of the Siegenian, possibly comes from a concentrate horizon. Early subspecies of I. huddlei occur in the Siegenian and develop progressively in the Lower and Upper Emsian. I. bilatericrescens and Polygnathus appear first in the Emsian. P. linguiformis s.s. and the I. corniger group are installed in the Upper Emsian. The lower boundary of the Middle Devonian is problematical, for Icriodus corniger, which gives its name to the lowermost conodont zone, occurs already in the Emsian. Occurrence of a new, unnamed Polygnathus and I. angustus s.s. indicate a further subdivision. The Spathognathodus bidentatus- and Polygnathus kockelianus-Zones are well established in the higher Eifelian. The I. obliquimarginatus-Zone (=new name for eiflius- and robusticostatus-Zones of Wittekindt) corresponds to Lower and Middle Givetian and is subdivided by Polygnathus latus and P. kluepfeli. The Polygnathus varcus-Zone, with three subdivisions, coincides with the Upper Givetian. At present, the Middle-Upper Devonian boundary coincides with explosive development of advanced polygnathids in the Schmidtognathus hermanni-Polygnathus cristatus-Zone. All major Upper Devonian zones of Ziegler's firmly established zonation are recognized world-wide and recent investigations relate them precisely to the standard ammonoid sequence. A new fauna, closely below the Carboniferous and above the Spathognathodus costatus-Zone, is named for Protognathodus (Ziegler, 1969b), based on Gnathodus kockeli Bischoff, 1957.

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