Late Givetian ammonoids from Hassi Nebech (Tafilalt Basin, Anti-Atlas, southern Morocco)

Abstract. The Hassi Nebech area of the SE Tafilalt (Tafilalt Basin, Anti-Atlas, Morocco) yielded the richest and most diverse late Givetian ammonoid fauna on a global scale. Above the distinctive regional "Lower Marker Bed" (Synpharciceras clavilobum Zone), abundant loosely collected limonitic specimens derive from hypoxic shales of the Taouzites taouzensis to Petteroceras errans zones. The ontogenetic morphometry and intraspecific variability of a total of 30 species representing five families, the Acanthoclymeniidae, Taouzitidae, Pharciceratidae, Petteroceratidae, and Tornoceratidae, are documented. New taxa are: Pseudoprobeloceras praecox n. sp., Scaturites minutus n. gen. n. sp., Darkaoceras velox n. sp., Pharciceras decoratum n. sp., Ph. fornix n. sp., Ph. subconstans n. sp., Ph. involutum n. sp., Lunupharciceras incisum n. sp., Transpharciceras procedens n. gen. n. sp., Stenopharciceras progressum n. sp., Pluripharciceras n. gen. (type species: Synpharciceras plurilobatum Petter, 1959), Plu. orbis n. sp., Synpharciceras frequens n. sp., Lobotornoceras bensaidi n. sp., Nebechoceras eccentricum n. gen. n. sp., and Phoenixites lenticulus n. sp. The documentation of conch and particularly suture ontogeny and intraspecific variability necessitates a revised diagnosis for ten taxa. Manticoceras pontiformis Termier & Termier, 1950, Probeloceras costulatum Petter, 1959, and Pseudoprobeloceras nebechense Bensaïd, 1974 are regarded as subjective junior synonyms of Ps. pernai (Wedekind, 1918). Sandbergeroceras acutum Termier & Termier, 1950 is a subjective synonym of Taouzites taouzensis (Termier & Termier, 1950). Pharciceras applanatum Bensaïd, 1974 is transferred to Extropharciceras. Other forms (Ph. aff. tridens, Ph. cf. subconstans n. sp., Extropharciceras n. sp. 2, Ex. cf. arenicum, Ex. cf. applanatum, Synpharciceras sp., Plu. cf. plurilobatum) are described in open nomenclature.

doi:10.1002/mmng.201300001