In the Umbria-Marche area, during the Sinemurian-Carixian, due to tectonic/eustatic events the carbonateplatform (Calcare Massiccio Fm) was drowned, and a basin with a differentiated topography was established. The pelagic sedimentation was represented at first by a calcareous lithofacies (Corniola Fm) and later on by a clayey and marly lithofacies (Marne del Monte Serrone Formation =MS). The sediments here considered belong to the lower part of the MS, and they are Late Domerian-Early Toarcian in age. The micropaleontological assemblages show a progressive deepening of the sedimentary environment from middle shelf to outer shelf-upper bathyal conditions. This trend is compatible with a general sea-level rise in the European and North African domains during the Early Toarcian. In the clayey and/or marly sediments of the Late Domerian-Early Toarcian, many foraminifers, such as Miliolina which are abundant in the Carixian, disappear or become very rare. Only Lagenina, both sculptured and smooth, survive and are associated with siliceous Glomospirella which are very common or dominant. The benthic foraminiferal assemblages are associated with large ostracods, macroinvertebrates, and often with thin flat bivalves. Within the MS sediments of the Tenuicostatum Zone, sculptured Lagenina and Glomospirella, decrease in size and abundance and finally disappear together with the bivalves, both in disaerobic-anoxic conditions and in aerobic environments. Their disappearance can be related to the deepening of the basin.