A B S T R A C T . Eifelian (Middle Devonian) ammonoids of the Pinacitinae Hyatt, 1900 (Exopinacites, Pinacites) with
 preserved shell structures from the eastern Anti-Atlas (Morecco) have revealed unusual morphological features.  The
 Pinacitinae belong to the earliest ammonoids which closed their umbilici.  As an approach to an interpretation of these
 structures, the representatives of the subfamily Pinacitinae (Exopinacites singularis, Pinacites jugleri, P. eminens) are
 compared with other ammonoids, e.g. Acrimeroceras, Araucanites, Clistoceras, Gaudryceras, Nathorstites, Prolo-
 bites, and Synpharciceras, which produced umbilical plugs and covers.  Some of these are comparable in structure to
 Nautilus pompilius and N. belauensis.  In contrast to all of these taxa, the lateral shell wall of the Pinacitinae reached the
 centre of the umbilicus and formed an umbilical lid.  The umbilical shell wall rests on the umbilical lid of the previous
 whorl.  This construction probably had the advantage that it improved the hydrodynamic properties of the conch, along
 with die oxyconic conch shape and the approximately horizontal orientation of the aperture.