The highest records of North American scaphitid ammonites in the European Maastrichtian (Upper Cretaceous) and their stratigraphic implications

Abstract

The uppermost lower to upper Maastrichtian records of North American scaphitid ammonites in Europe are discussed in terms of taxonomy and significance for transatlantic correlation. A previous record of a U.S. Western Interior scaphitid ammonite, Jeletzkytes dorfi, from the lower part of the upper Maastrichtian in northeast Belgium, is demonstrated to have been based on specimens which reveal features typical of the indigenous European Hoploscaphites constrictus lineage. However, one of the individuals in this collection combines distinct mid-ventral swellings, characteristic of the H. constrictus stock, with irregular flank ornament, typical of J. dorfi. It is speculated that this specimen may be a product of interspecies hybridization. Hoploscaphites sp., allied to H. nicolletii or to H. comprimus, previously known only from the U.S. Western Interior, is recorded from the lower upper Maastrichtian of Austria, and Discoscaphites gulosus, hitherto regarded to be confined to the U.S. Western Interior, Gulf Coast, and Atlantic Seaboard, has been recognised in the upper Maastrichtian of Bulgaria. Additionally, poorly preserved material referred to as Discoscaphites? sp. is recorded from the uppermost lower Maastrichtian of Denmark, and from the upper Maastrichtian of southern Sweden. These records of scaphitids support earlier conclusions that the base of the European upper Maastrichtian roughly corresponds to the base of the Hoploscaphites birkelundae Zone in the U.S. Western Interior.