Ammonites from the Saratoga Chalk (Upper Cretaceous), Arkansas

The Saratoga Chalk of Arkansas yields a rich ammonite fauna of 17 species, referred to theNostoceras(N.)hyattizone. Recognition that the northwest EuropeanN.(N.)pozaryskiiBlaszkiewicz, 1980, is a synonym ofN.(N.)hyattiStephenson, 1941, andN.(N.)helicinum(Shumard, 1861) dates the zone as latest Campanian on the basis of co-occurrence withBelemnitella langeiJeletzky, 1948, in Poland. Most previous estimates of the Campanian–Maastrichtian boundary in the Gulf Coast have been drawn at too low a level, at least in terms of ammonite faunas. Elements of theN.(N.)hyattizone fauna occur in the United States Western Interior, and show the base of the Maastrichtian there to lie above theBaculites jensenizone.