Elena Koleva-Rekalova

The Ammonites of the Bifrons Zone (Toarcian, Lower Jurassic) from Mihailovići (Northern Montenegro)

The base of the red pelagic nodular limestones exposed near the Mihailovići Pass (Northern Montenegro) yielded condensed Toarcian fossil assemblage consisting uniquely of ammonites. The ammonites were collected from marker horizon associated with prominent hardground surface. This assemblage is composed both of species of worldwide distribution and proper Tethyan dispersal. It includes frequent Lytoceratina and common Phylloceratina and Ammonitina. The latter allowed the biostratigraphic definition of the fossiliferous horizon as mid-Bifrons Subzone of the Lower Toarcian Bifrons Zone. Thirteen ammonite taxa were studied: Phylloceras heterophyllum (Sowerby), P. prinzi Géczy, Calliphylloceras nilssoni (Hebert), Lytoceras toarcense Rulleau, Nodicoeloceras angelonii (Ramaccioni), Hildoceras lusitanicum Meister, H. bifrons (Bruguière), Cingolites aff. picenus Sassaroli & Venturi, Osperleioceras subexaratum (Bonarelli), Harpoceras mediterraneum Pinna, Phymatoceras anomalum Merla, Ph. gr. narbonense Buckman and Ph. cf. formosum Rulleau & Elmi. One specimen was defined as Harpoceras sp. n. since it did not match any species from the literature, but might be erected as a new specific name if further materials appear.