La faune ammonitique des marnes à fossiles ferrugineux de la région de Niort, France (Oxfordien inférieur, Zone à Cordatum, Sous-Zone à Cordatum) [The ammonite fauna of the 'marls with ferruginous fossils' from the Niort region, France (Lower Oxfordian, Cordatum Zone, Cordatum Subzone)]

A new collection of ammonites from the 'marls with ferruginous ammonites' in the Niort region (France), previously studied by Grossouvre (1922), provides a large amount of biostratigraphic, paleoenvironmental and paleogeographic information. The fauna is dated Early Oxfordian: Cordatum Zone, Cordatum Subzone, probably the lower part of it. In addition, it is unique in western Europe owing to: 1) the species found of which some appear to be known only in this deposit 2) by the extremely atypical domination of the couple Taramelliceras - Creniceras which represent 2/3 of the specimens. Furthermore, the aspect of the fauna strongly suggests that the habitat was a distal platform unknown in other European strata of the same age. A detailed description of the several species is given, sometimes accompanied by a new taxonomic interpretation