Upper Silurian and Lower Devonian conodonts from Tafilalt, southeastern Morocco

Abstract

The conodont association from three Silurian-Lower Devonian sections (Bou Tchrafine N2, Atrous 3 and Atrous 7) in the Tafilalt (southeast Morocco) are presented. The sections are constituted by cephalopod rich limestones ("Orthoceras limestones") and by crinoidal limestones ("Scyphocrinites limestones") cropping out within thick shaley sequences. The association includes 29 taxa belonging to 13 genera (Ancyrodelloides, Belodella, Dvorakia, Icriodus, Kockelella, Lanea, Oulodus, Ozarkodina, Pelekysgnathus, Polygnathoides, Pseudooneotodus, Wurmiella, Zieglerodina). The conodont fauna allows the recognition of seven conodont zones: ploeckensis and siluricus in the Ludlow, eosteinhornensis s.l., Lower detortus and Upper detortus in the Přídolí, and hesperius and transitans in the Lochkovian. The age of the "Orthoceras limestones" is confirmed as middle Ludfordian (ploeckensis-siluricus zones), whereas it is stated that the "Scyphocrinites limestones" spans the Silurian/Devonian boundary. Some elements of the apparatus of Zieglerodina planilingua and the P2 element of Lanea omus are described. The phylogenetic relationships between genera Lanea and Ancyrodelloides are discussed.•

Lower Lochkovian (Lower Devonian) conodonts from Cellon section (Carnic Alps, Austria)

“…planilingua Murphy & Valenzuela-Ríos to Ziglerodina. The assignment of the latter species to Zieglerodina has been confirmed by Corriga et al (2014) on the basis of the reconstruction of the apparatus. Corriga (2011) considered Ozarkodina eladioi (Valenzuela-Ríos) as a species of Zieglerodina.…”

First documentation of the Polygnathoides siluricus conodont Zone (Ludfordian) in South America (Argentina) and the stratigraphic significance of the younger species of Kockelella (Conodonta)

“…On the other hand, in the last section, K. o. sardoa occurs up to the central part of the zone, and K. maenniki slightly higher, whereas in the nearby Genna Ciuerciu section (Corradini, Ferretti, Corriga, & Serpagli, ; Corradini, Ferretti, Serpagli, & Barca, ), these taxa have a contemporaneous last occurrence, about 2 m below the top of the P. siluricus Zone. Recently, Corriga et al () recorded K. v. variabilis and K. v. ichnusae only in the lower part of the P. siluricus Zone in Morocco, whereas K. maenniki is not documented up to now in this region (Figure ).…”

“…K . v. variabilis was once supposed to have become extinct in the uppermost part of the A. ploeckensis Zone (Barrick & Klapper, ; Serpagli & Corradini, ) but has been recently documented in the lower part of the P. siluricus Zone (e.g., Corradini et al, ; Corriga et al, ; Slavík et al, ). The other species of Kockelella present at Poblete creek section occur in the P. siluricus Zone, even if their last occurrences are documented at different stratigraphic levels within this biozone.…”

“…From the K. crassa Zone to the lower part of the P. siluricus Zone (Corriga, Corradini, & Walliser, 2014).…”

“…The Ludfordian species of Kockelella are widely recorded and studied in different regions around the world and show their last occurrence at various levels within the P. siluricus Zone. K. v. variabilis was once supposed to have become extinct in the uppermost part of the A. ploeckensis Zone (Barrick & Klapper, 1976; but has been recently documented in the lower part of the P. siluricus Zone (e.g., Corradini et al, 2015;Corriga et al, 2014;Slavík et al, 2010). The other species of Kockelella present at Poblete creek section occur in the P. siluricus Zone, even if their last occurrences are documented at different stratigraphic levels within this biozone.…”