Evolution of Rudist revealed by their shell micro sturucture

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Rudists are a group of mainly sessile bivalves with peculiar shell forms, which lived in the Mesozoic Era arid especially between Jurassic and Cretaceous Periods in so called Thethysan Region. The group enjoyed their prosperity during the time. Their fossils occur abundantly from carbonate plat-form environments, and were an important element as organic builder. The group appeared as one family in the late Jurassic, then during the Cretaceous Period it diversified into 6 families including 100 genera.In the present study, the peculiar morphology of the group as well as peculiar shell structure was investigated.To do so material in Vienna University as well as in Natural History Museum, Vienna, Austria was examined. Also several important localities of the Rudist fossils was visited and examined in Germany, Austria, and Slovenia as well as northern Italy.Finally a classic Text book on this theme, "Rudists and facies of the Periadriatic Domain" written by Cestari, R. and Sartorio, D. (1995) (published by Agip, S.p.A., S. Donanto Milanese) was translated into Japanese to stimulate the study on this topic by Japanese paleontologists.