Stephanoceras humphriesianum (Ammonoidea), an Index Species of the Lower Bajocian, in the Basin of the Kuban River (Northern Caucasus, Russia)

The paper discusses Stephanoceras humphriesianum (J. de C. Sowerby), an index species of the upper zone of the Lower Bajocian (Middle Jurassic) standard scale, identified for the first time from the lower subformation of the Djangura Formation of Karachay-Cherkessia. The fixation of the lectotype of Ammonites humphriesianus is discussed. New finds make it possible to establish the humphriesianum faunal horizon in the middle part of the eponymous zone for the Kuban River basin.