A revision of the ammonite faunas of the type Cenomanian. i. Introduction,ancyloceratina

This paper forms the first part of a revision of the ammonite faunas of the Cenomanian stratotype in the environs of Le Mans, Sarthe, France. The history of research on ammonites in the area is briefly noted, as is the lithostratigraphy. The systematics of the heteromorph ammonites (Ancyloceratina) is described, and the following taxa documented: Hamites simplex d'Orbigny, Sciponoceras baculoides (Mantell), Sciponoceras gracile (Shumard), Anisoceras plicatile (J. Sowerby), A. aff. plicatile, Idiohamites alternatus vectensis Spath, I. ellipticus radiatus Spath, Hypoturrilites gravesianus (d'Orbigny), H. tuberculatus (Bosc), H. mantelli (Sharpe), H. sp., Neostlingoceras carcitanense (Matheron), N. aff. carcitanense, Turrilites costatus Lamarck, T. acutus Passy, T. scheuchzerianus (Bosc), T. boerssumensis Schlüter, Mariella dorsetensis (Spath), M. cenomanensis (Schlüter), M. group of cenomanensis (Schlüter)-lewesiensis (Spath), M. spp., M. (Plesioturrilites) sp., Scaphites equalis J. Sowerby, S. obliquus J. Sowerby, S.(?) sp., and S. sp. juv.