Giant Bathysiphon (Foraminiferida) in the building stones of the Priamar Fortress (Oligocene, Savona).

Large and well-preserved specimens of agglutinated foraminifera, specifically Bathysiphon palachei, have been identified in the building stones of the Priamar Fortress located in Savona, Liguria, NW Italy. These specimens, with test lengths extending up to 120 mm, are among the largest foraminifera documented to date. We identified the source of the building stone as the Costa Quarry, located near Bedonia, where the Monte Zuccone Sandstone (Chattian-Aquitanian) is exposed. However, Bathysiphon specimens are now scarcely observable in the original quarry due to extensive quarrying activities over the past four decades, which have substantially depleted the original foraminifera-bearing horizon. Thus, the Priamar Fortress represents an important geoheritage site for the study and appreciation of these remarkable foraminifera, which are otherwise rarely encountered in their source outcrop. The Monte Zuccone Sandstone displays a diverse array of trace fossils, including abundant Halopoa imbricata and graphoglyptids (Paleodictyon minimum, Spirorhaphe involuta, and Desmograpton? ichthyforme), in addition to Ophiomorpha annulata, Helminthopsis? labyrinthica, and Scolicia strozzii. Considering the ichnological association, alongside taphonomic and sedimentological observations, it is suggested that the studied Bathysiphon were deposited in a deep-sea fan environment after experiencing minimal transport. Low-oxygen conditions likely favoured preservation of these specimens. The Priamar Fortress represents a significant geoheritage site, warranting the development of a valorisation and conservation program. Its building materials provide a unique context for the study and dissemination of paleontological knowledge, offering insights that surpass those available from known natural outcrops or museum specimens.