Breaking two decades of silence: new data on Barremian ammonites from dysoxic layers of the Maiolica Fm. (Umbria–Marche Basin, Central Italy)

The Umbria–Marche Basin has long represented a cradle of ammonite research. Already the first generation of pioneers (e.g., Fucini, Canavari, Zittel, Meneghini) focused on the fossil-rich Jurassic successions while the Lower Cretaceous deposits (Maiolica Fm.) remained comparatively neglected due to the general rarity and poor preservation of the specimens. A turning point came in the late 1980s, when the ammonite-based biozonation spanning the Berriasian–Barremian was established by Cecca, Pallini, Faraoni and Marini. From the early 2000s onward, research activity progressively ceased, leaving the Lower Cretaceous ammonite knowledge of the Umbria–Marche area largely stagnant until the 2020s. Renewed investigations have enhanced our understanding of distinctive dysoxic layers (Conti et al., 2025 and unpublished data), providing new insights into their origin and significantly advancing the study of the ammonite assemblages that distinctly characterize them. The most significant results include: a) The discovery of abundant Leptoceratoididae in several horizons spanning the N. pulchella-T. vandenheckii Zones (lower/upper Barremian), across multiple sections; b) The first report of the genera Deitanites, Moutoniceras and Euptychoceras as well as of the species Leptoceratoides ternbergense, Karsteniceras cf. hoheneggeri, Holcodiscus decorus H. nodosus, H. cf. diversecostatus, A. aff. cadoceroides and Kotetishvilia sauvageaui. The recognition of several Leptoceratoididae-rich horizons demonstrates that this family was locally abundant also on the Adria microplate. Comparable occurrences in Austria (Lukeneder, 2005) and Hungary (Gőgös & Szives, 2024), together with their proposed ecological significance (Conti et al., 2025), provide key constraints for regional paleoecological considerations. Moreover, the identification of previously unreported taxa in the Umbria–Marche Basin provides robust biostratigraphic and paleobiogeographic links with major European reference areas (e.g., Vocontian Basin, Subbetic and Prebetic domains, Transdanubian Range), suggesting that this basin preserve an integral component of the Early Cretaceous Mediterranean Tethyan paleobiogeographic mosaic.