Quereilhac P., Marchand D., Jardat R., Bonnot A., Fortwengler D., Courville P. (2009) La faune ammonitique des marnes a fossiles ferrugineux de la region de Niort, France (Oxfordien inferieur, Zone a Cordatum, Sous-Zone a Cordatum) // Carnets de Geologie. Article 2009/05. 21 pp.
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, paeleoenvironmental and paleogeographic information. The fauna is dated Lower 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" [=Glochiceras?] 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 [NB: Tramelliceratid-dominated assemblage from the Cordatum Zone (Taramelliceras - Glochiceras jeanneti attain more than 90% of the whole assemblage!) has been reported previously from the Saratov Volga area, Central Russia, by Rogov & Egorov, 2003]. A detailed description of the several species is given, sometimes accompanied by a new taxonomic interpretation