THE DIMORPHISM OF THE GENUS ERMOCERAS DOU VILLE, 1916 (STEPHANOCERATIDAE, LATE BAJOCIAN) AND NOMENCLATURAL IMPLICATION

New insights on dimorphism of Ermoceras are provided by the study of p artly new and unpublished material from Sinai, Saudi Arabia, Morocco a nd Algeria. Two types of dimorphism are recognized among representativ es of Ermoceras. However, the evaluation of dimorphism in E. mogharens e, the type species of Ermoceras remains unclear because of poor docum entation. The dimorphic pair of Telermoceras (E. coronatoides-coronati forme group) has a contracted body-chamber with a simple aperture endi ng with a ventral rostrum in the macroconch only. In platycone Kosmerm oceras the mature microconch has a ribbed body-chamber with lateral pa ired lappets, whereas the mature macroconch has a smooth body-chamber with a probable simple aperture. In our view, Telermoceras must be dis tinguished from other representatives of Ermoceras (i.e. Ermoceras s.s . et Kosmermoceras).