A rare occurrence of Late Hettangian ammonites (Angulaticeras and Paracaloceras) in the Mediterranean Tethys (Rif, Northern Morocco)

This paper describes and illustrates three newly discovered Late Hettangian ammonite specimens from the “Dorsale calcaire” (Calcareous Range) of the internal units of the Rif (Northern Morocco). Two additional Early Sinemurian ammonite specimens are also studied and all the Early and middle Lower Jurassic ammonites collected earlier in this area and illustrated in the literature are included in order to clarify the biostratigraphical and palaeobiogeographical framework. The Late Hettangian Moroccan assemblage which includes Angulaticeras marmoreum (OPPEL, 1862) and Paracaloceras haueri (GÜMBEL, 1861) is close to the coeval faunas which have been known since the 19th century in several famous fossiliferous localities of the Northern Calcareous Alps (NCA). These faunal similarities support the palaeobiogeographical hypothesis which supposes the existence, during the Jurassic, of a “Mesomediterranean terrane” or “ALKAPECA micro-continent” which is currently dislocated. The Betic, Rif, Kabylia and Peloritani “Dorsales” are fragments of this former micro-continent. This hypothesis suggests that the “Dorsale [...] DOMMERGUES, Jean-Louis, MEISTER, Christian, WILDI, Walter. A rare occurrence of Late Hettangian ammonites (Angulaticeras and Paracaloceras) in the Mediterranean Tethys (Rif, Northern Morocco). Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, 2010, vol. 256, no. 3, p. 335-351 DOI : 10.1127/0077-7749/2010/0057