The ammonite genera Gravesia Salfeld and Pseudogravesia Hantzpergue in the Tithonian of S Germany and their correlation value with Western Europe

The Subboreal ammonite genus Pseudogravesia and new finds of the genus Gravesia are reported from the Tithonian of Swabia. In S Germany Gravesia is widespread in the middle part of the Hybonotum Zone (riedlingensis to laisackerensis horizons), but does not occur in the end of the zone. The older level with Gravesia gigas (riedlingensis Horizon) can be identified in Franconia and SE France as well. This horizon corresponds to the lower part of the gigas Horizon (Gigas Zone) in W France. There, a higher level yielding both G. gigas and G. gigas intermedia corresponds with the beds between the riedlingensis and laisackerensis horizons in Swabia. In the still younger Gravesiana Subzone of Quercy (W France) there exist two levels with Gravesia. The lower one contains Gravesia gigas intermedia and Gravesia gravesiana. The upper one yields exclusively G. gravesiana and very rare Pseudogravesia gravesiformis. The lower level corresponds to the laisackerensis Horizon of S Germany (numerous G. gigas intermedia, few G. gravesiana). All records of Pseudogravesia from Swabia come from the laisackerensis Horizon and belong to a single taxon. In the lower parts of the Hangende–Bankkalke Formation of Swabia, both Gravesia and Pseudogravesia are apparently missing. Younger faunal horizons of the Hybonotum Zone occur in Franconia but not in Swabia due to post-Jurassic erosion. In the ammonite faunas of the latest Hybonotum Zone of Franconia, above the laisackerensis Horizon, Submediterranean taxa predominate. This explains the lack of Gravesia and Pseudogravesia both in the rueppellianum and moernsheimensis horizons.