Late Cambrian to earliest Ordovician (Ibexian) conodont evolution and biogeography of Greenland and northwest Scotland

The Late Cambrian to earliest Ordovician coniform-dominated conodont faunas recovered from the platform carbonate sequences of western North Greenland, central East Greenland, and northwest Scotland comprise a total of22 multi-element genera. Four genera and seven species are new to this study. Although the faunas exhibit a strong North American Midcontinent Province affinity, a FranklinianlArctic fauna (typified by Pagetopetalon gen. nov. and Loxognathodus Ji and Barnes) has also been identified - a fauna which was restricted to the margins ofthe Laurentian craton (Greenland, northwest Scotland, western Newfoundland, and the Canadian Arctic Islands). Furthermore, conodonts recovered from the upper Eilean Dubh Formation of northwest Scotland, traditionally considered to be faunally barren, have unequivocally established an Ordovician (c. lindstromi Biozone) age; thus placing the Cambrian-Ordovician boundary at an interval within the formation. Revised apparatus reconstructions have been proposed for three genera: A septimembrate apparatus is proposed for Variabiloconus bassleri (Pander), and its homology with that of the Fauna 0 taxa Aloxoconus stauffiri (Furnish), Colaptoconus quadraplicatus (Branson and Mehl), Eucharodus parallelus (Branson and Mehl) and Ulrichodina deflexus Furnish, has significant implications regarding the actual diversity of samples over this interval. In contrast, Rossodus Repetski and Ethington is reconstructed with a quinquemembrate apparatus ofprioniodontid affinity (based on P element morphology). A trimembrate, crushing apparatus has also been proposed for Clavohamulus Furnish as a consequence of its comparative morphology with certain species of the Raja.