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1 2006

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New studies on perisphinctids from the Lower Tithonian (Hybonotum Zone) of S Germany and SE France

Scherzinger A., Atrops F., Schweigert G.

Volumina Jurassica

2006

Vol. 4, no. 1

244-245

New extensive collections from the Hybonotum Zone of Liptingen (SW Germany), Canjuers (Dpt. Var, France) and Crussol (Dpt. Ardeche, France), together with already published material from Laisacker (Franconia, S Germany, Schairer & Barthel 1981) give deep insights in ontogeny, intraspecific variation, dimorphism, and evolution of several Late Jurassic perisphinctid ammonite genera, as a basis for future revisions. In older studies perisphinctids were often problematic due to little material, erroneous interpretations of type species, incompletely or poorly preserved specimens, disregarding of dimorphism, and widespread homeomorphism. After our recent study the perisphinctids are much more diverse than previously thought. A correlation with French biohorizons established in the Paris and Aquitaine basins is possible due to the occurrence of Gravesia M+m and Tolvericeras M+m?, especially at Liptingen. Besides the two latter genera we can distinguish five other dimorphic pairs which are coupled as follows: Lithacoceras Hyatt (M) + Silicisphinctes Schweigert & Zeiss (m); group of "Virgatosphinctes" eystettensis Schneid (M) + Subplanites group A (m); Euvirgalithacoceras Zeiss, Schweigert & Scherzinger (M) + Subplanites group B, S. rueppellianus sensu Schairer & Barthel non Quenstedt (m); Hegovisphinctes Zeiss, Schweigert & Scherzinger (M) + group of "Torquatisphinctes" filiplex Schairer & Barthel non Quenstedt (m); Hoelderia Ohmert & Zeiss (M) + group of "Subdichotomoceras" sp. in Schairer & Barthel 1981, pl. 5, fig. 4 only (m). Some of these dimorphic pairs can be recognized also in SE Spain (Calanda area) and in the Balkans (Bulgaria, Croatia) and thus permit correlations across the Submediterranean Province. The rich perisphinctid fauna, together with other excellently preserved ammonites underlines the potential of the French sections as key sections for long-distance and high time-resolution correlations as well as the understanding of the Kimmeridgian-Tithonian transition.