The genus Lithancylus Casey, 1960 (Ammonoidea, Ancyloceratina) in the Lower Aptian of the Rhone Corridor (Drôme,
Southeast of France) - A rich ammonite fauna have been collected in the lower Aptian of the Rhone Corridor (Southeast of France)
in the vicinity of Pierrelatte and Bourg-St-Andéol. This fauna, dated from the Weissi zone by its fauna of Deshayesites, has delivered
heteromorphic ammonites of the genus Lithancylus Casey, 1960, which the representatives were not known until today with certainty
in the Southeast of France. The lower Aptian deposits in which have been collected the ammonite fauna is constituted by glauconitic
marls and limestones which are transgressive on the urgonian limestones of the Ardèche platform.
Two species of Lithancylus are described and figured in this work: L. godeti (Thieuloy, 1990) and L. renatae sp. nov. The comparison
between these two species and the other taxa belonging to this genus shows a more important size in the french samples and, in
the case of Lithancylus renatae nov. sp., a more premature end of the phragmocône and an ornamentation of the crozier close to
those observable within certain taxa of Ancyloceratidae as “Ancyloceras” renauxianum d’Orbigny, 1842. All these morphological
peculiarities still very “ancyloceratic” could be the indication that the forms described in this work, and quite particularly Lithancylus
renatae nov. sp., represents older forms inside Lithancylus Casey, 1960. The content of the genus is also discussed.