Cenomanian gastropods of Bellezma-Aures mountains (Batna, NE Algeria): Taxonomy, palaeoecology and palaeobiogeography

Twenty-one gastropod species are identified from the Cenomanian deposits of Bellezma-Aures mountains, eastern Saharan Atlas, Algeria. Among of these taxa four species [Tylostoma elevatum (Shumard), T. torrubiae Sharpe, Nerinea olisiponensis Sharpe and Calliomphalus orientalis Douville '] are recorded for the first time in the mounts of Batna. These gastropods taxa are found scattered in the 'Marnes de Smail' Formation and their community changes can be attributed to minor sea-level fluctuation associated to variation in the sedimentation rate and hydrodynamics. Furthermore, the palaeobiogeographic distribution of these gastropod assemblages display tethyan affinity and their subsequent faunal exchange in that time interval.