A note on reiterated phenotypes in species of Neogastroplites (Ammonoidea,Cenomanian, Cretaceous)

Three North American species of the ammonite genus Neogastroplites from the Cenomanian of the Western Interior encompass several morphological variant s that are so similar from species to species that without prior knowledge of the stratigraphical location of some, it is not possible to make a certa in identification by standard methods of ammonite taxonomy. The application of methods of traditional morphometrics to shape-criteria leads to an obje ctive appraisal of the situation and a reduction in the possibilities of co nfusion in specific assignations. Ornamental features, although not incorpo rated in the shape-data, are shown to be in part linked to the shape-status of the shell. (C) 2000 Academic Press.