The heteromorph ammonite genus Ancyloceras (Ancyloceratidae) in the Paris Basin (lower Aptian, Lower Cretaceous, NE France)

In the present work, we examine a sample of 54 specimens of the heteromorph ammonite genus Ancyloceras d’Orbigny, 1842 from the Argiles à Plicatules Formation (lower Aptian, Lower Cretaceous) of the eastern Paris Basin (NE France). The results are as follows: (1) the sample is regarded as monospecific and assigned to the well-named species Ancyloceras varians d’Orbigny, 1842; (2) its variability is continuous and concerns as well as adult size,...