Early Toarcian (Jurassic) belemnites from northeastern Gondwana (South Riffian ridges, Morocco)

摘要

A belemnite fauna collected in the lowermost Toarcian succession that crops out near Moulay Idriss (northern Morocco) is studied in this article. This is the first palaeontological study of Early Toarcian belemnites from Northern Africa, i.e., the northeastern margin of the Gondwana, in connexion with Tethys. Four species of the family Passaloteuthidae Naef, 1922, have been identified: Passaloteuthis bisulcata (de Blainville, 1827), Pseudohastites longiformis (Blake, 1876), Parapassaloteuthis zieteni (Mayer-Eymar, 1884) and Parapassaloteuthis sp. A. All species have been collected in lowermost Toarcian beds dated to the ammonite Polymorphum Chronozone (=Tenuicostatum Chronozone), which coincides with the belemnite Passaloteuthis bisulcata biozone. The discovery of a syntype of this zonal index is discussed. The identified species are common with Europe, thus suggesting that the onset of the belemnite provincialism in the Toarcian could post-date the earliest Toarcian Polymorphum-Tenuicostatum Chronozone. However, records of Early Jurassic belemnites are still too sparse to recognize the establishment of provincialism and the timing of its onset.