The giant, up to 40 cm high littorinoid gastropods from the Middle Tithonian to Berriasian carbonates of the Alpine- Carpathian northern Tethys margin are assigned to the genus Leviathania. The genus is distributed from Spain to the Caucasus. Some species formed dense populations in the wide-spread, highly productive lagoonal environments situated on the carbonate platforms of Ernstbrunn (Austria), Mikulov, Štramberk (both Czech Republic), and Nyzhniv (Ukraine). The conspicuous morphology, comprising very large shells with strongly angulated whorls and especially the phaneromphalous umbilicus exclude the traditional attributions of this genus to the families Purpurinidae and Purpuroideidae. Therefore, we establish the new family Leviathaniidae for the type genus Leviathania. The family comprises the largest pre-Cenozoic gastropods, represented by a yet unnamed gigantic Leviathania species from the latest Tithonian or early Berriasian of Ukraine. The gastropods are tentatively assumed to have fed omnivorous, i.e., on a mixed detrital-algal diet, based on comparable population densities as the large modern queen conch Lobatus gigas from the Caribbean Sea.

Key words: Mollusca, Gastropoda, Leviathania, carbonate platform, body size, Tethys, Tithonian, Ernstbrunn Limestone, Austria.

Mathias Harzhauser [mathias.harzhauser@nhm-wien.ac.at], Geological-Paleontological Department, Natural History Museum Vienna, Burgring 7, A-1010 Vienna, Austria; Simon Schneider [simon.schneider@casp.cam.ac.uk], CASP, University of Cambridge, West Building, 181A Huntingdon Road, Cambridge CB3 0DH, UK.