A New Llandovery (Early Silurian) Conodont Biozonation and Conodonts from the Becscie, Merrimack, and Gun River Formations, Anticosti Island, Québec

An abundant conodont fauna was recovered from 202 samples taken from the Becscie, Merrimack, and Gun River formations of early Llandovery (Early Silurian) age on Anticosti Island, Québec. From the collection of 22,409 identifiable specimens, 28 species and four associations representing 12 genera and one group of drepanodontiform elements are documented and their stratigraphic ranges established. One new genus, Rexroadus, is established for two species earlier assigned with question to Oulodus. New species described are Icriodella dicrana, Oulodus sigmoideus, Ozarkodina strena, and Pterospathodus? originalis. The fauna is dominated by species of Ozarkodina and Oulodus; many species have a first appearance that is slightly older than elsewhere suggesting that the Anticosti Basin may have been an important evolutionary radiative center in the early Silurian. There is a slow and progressive diversity increase in conodonts through this interval after the initial appearance of many new taxa in the basal Silurian following the mass extinction in the terminal Ordovician. The Anticosti Llandovery sequence represents one of the few highly fossiliferous, continuous successions in the world and a new conodont biozonation based on conodonts for the Llandovery is proposed with the following interval zones in ascending order: Ozarkodina hassi (new), Ozarkodina strena (new) [subdivided into Oulodus jeannae (new) and Oulodus panuarensis (new) subzones], Ozarkodina clavula (new), Ozarkodina aldridgei (new), Pterospathodus celloni, and Pterospathodus amorphognathoides zones.