Fossil testate amoebae and their non-marine finds are rare so their ecological importance through Earth history is poorly understood. The Lower Jurassic shallow water black-shales of Trento Platform (north-east Italy) are rich in micro-organisms and contain a thecamoebian and ostracod assemblage representing the first known record of Early Jurassic oligohaline forms from the European mainland. The thecamoebians are represented by the genera Difflugia, Pontigulasia and Centropyxis. The present discovery of Lower Jurassic thecamoebians in fine carbonate organic-rich deposits indicates, for the first time, that these sediments can preserve testate amoebae very well. The occurrence of difflugid testate amoebians confirm a transitional marine-terrestrial habitat, outside large bodies of water, and suggests occasional eutrophication in ephemeral restricted aquatic environment in the Sinemurian-Pliensbachian Trento Platform.
The rich fossil content of the Lower Jurassic carbonate successions of the Trento Platform (northeastern Italy) have been studied since the beginning of the nineteenth century. This detailed study on several stratigraphic sections cropping out in this area, all spanning the Liassic Rotzo Member (Calcari Grigi formation, Venetian Prealps), provides us new biostratigraphic data about the genus Everticyclammina Redmond 1964. A new species of Everticyclammina, E. praevirguliana n. sp., is formally described from the Calcari Grigi, where it occurs in levels attributed to the late Sinemurian to Domerian age. Everticyclammina praevirguliana n. sp. thus becomes the first representative of the genus in the Early Jurassic; this record consequently enables the stratigraphic distribution of the genus to be lowered to the Liassic. Hence the plexus of Everticyclammina evolving communities now bridges the Liassic (late Sinemurian) to Early Cretaceous (Aptian) interval.
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