New upper Givetian to basal Frasnian conodont faunas from the Tafilalt (Anti-Atlas, Southern Morocco)

Abstract

Conodont faunas, mostly from previously unsampled sections of the Tafilalt (eastern Anti-Atlas, Morocco) and spanning the upper Givetian to basal Frasnian, include first records of species for the region and NW Gondwana as well as new taxa: "Ozarkodina" maroccanica n. sp., Polygnathus aequidivisus n. sp., Po. dengleri sagitta n. ssp., Po. jorfensis n. sp., Po. saevus n. sp., Po. tafilensis n. sp., and Schmidtognathus longicavus n. sp. The morphology of Tortodus subsymmetricus n. sp. suggests relationships of Tortodus with Frasnian ancyrognathids. Other taxa are described in open nomenclature: Po. cristatus n. ssp., Icriodus aff. I. symmetricus, Skeletognathus aff. Sk. norrisi, and enigmatic supposed Pb elements (Gen. et sp. indet.). Ctenopolygnathus lanei Kuzmin (1995) is emended and distinctive morphotypes are recognized in Ct. angustidiscus and Po. collieri. Mesotaxis falsiovalis Sandberg et al. (1989) is a subjective junior synonym of the widely overlooked M. guanwushanensis (Tian, 1988). The revised regional lithostratigraphy and conodont sequences allow to refine the upper Givetian zonation. The former Upper disparilis Zone is subdivided into successive Po. dengleri sagitta and Po. dengleri dengleri subzones. The basalmost Frasnian Ancyrodella rotundiloba pristina Zone (= MN 1 Zone) is preserved as a thin, condensed limestone just at one locality (Bine Jebilet). The overlying Frasnes Event Beds (Lower Styliolinites) seem to fall in the subsequent Ad. rotundiloba soluta Zone (MN 2 Zone). Records of rare taxa, such as Po. paradecorosus, Po. pollocki Morphotype 1, oldest Po. webbi, Ct. angustidiscus, and Ct. lanei may be helpful for correlation into distant areas or shallower facies.