Late Cretaceous Ammonites from Central Saudi Arabia

Eight ammonite species from the Khanasir Limestone Member and the overlying Hajajah Limestone Member of the Aroma Formation in Central Saudi Arabia have been described and illustrated. Their ages and comparison with similar species are presented here. These ammonite species consist of Pachydesmoceras sp., Pachydiscus (Pachydiscus) launayi (deGrossouvre), Metatissotia cf. ewaldi (Von Buch). Hemitissotia turzoi Karrenberg, H.arumaensis sp. nov., Manambolites amardi Collignon and Roman. Libycoceras chargense Blankenhorn and Libycoceras sp. According to these ammonite species, the Khanasir Limestone Member is dated as Middle-Late Coniacian to Middle Campanian. The overlying Hajajah Limestone Member is dated as Upper Campanian. Tectonic tilt and possible global sea level drops during Late Coniacian are responsible for a hiatus and this includes Santonian-Lower Campanian in Cen-tral Saudi Arabia. The Campanian-Maastrichtian boundary in ammonite terms in Central Saudi Arabia is drawn here at a different level rather than on larger forams as it was previously based on