There is more than meet the eyes: unfolding the diversity, age, and ecology of the Late Cretaceous Villaggio del Pescatore site (Trieste, Italy)

The Late Cretaceous Mediterranean archipelago, its geodynamic history, ecological diversity, paleogeography and faunal composition stand as one of the most complex and debated topics related to the evolution of the Tethys Ocean and its continental margins. We conducted a pilot project started in 2019, generating novel and unforeseen outcomes related to one of the most important fossil localities of Europe: the Villaggio del Pescatore site (VdP, Duino-Aurisina, Trieste, Italy). Although this locality has achieved notoriety for the exquisite preservation of its dinosaur-dominated fossil assemblage, the organization of historically neglected and newly re-evaluated data into a unified framework set the ground for a renewed understanding of this site. With more than 450 identifiable fossils (including fish, crocodilian, dinosaurs, pterosaurs, crustaceans, plant remains, invertebrates), microfossils (foraminifera, pollens, ostracods, cyanobacteria), ~200 thin sections for biostratigraphic analyses, more than 100 still unprepared specimens and other still found in situ, the VdP offers a unique, high-resolution window for qualitative and quantitative analyses, including a detailed redefinition of its age. New prospecting activities and extractive processes resulted in additional observations. We here reevaluate data presented in the literature as referring exclusively to a very restricted area of approximately 300 square meters of the quarry and document that less than 40% of the site has been so far mapped and support a continuous extension of fossil beds outside the main, protected area. From a sedimentologic perspective, the uniqueness of VdP is represented by sharp facies variations from open marine, shallow-water limestones to organic-rich rhythmites, which interbed with breccias that accumulated as underwater bodies of breccia by subaqueous, density-driven, sedimentary flows. Rhythmites and breccias are folded by slumping and deformed by wet-sediment normal fault. Slumps also raise questions concerning the taphonomy (preservation of land vertebrates in dysoxic to anoxic bottom waters from marginal-marine settings) as well as the interaction between different depositional settings (terrestrial-paralic–shallow marine). The outstanding example of ‘Bruno’ – the second, sub-complete Tethyshadros insularis extracted from the quarry – shows how the mesoscale folding has interested the fossil body harmoniously but maintaining most of its skeletal connections. Based on inventory and new field surveys, we estimate seven articulated skeletons preserved at the VdP site and possibly eleven individuals of T. insularis. Originally described as an insular, pygmy hadrosauroid closely related to hadrosaurids, based on a single specimen. T. insularis is here revised on the basis of multiple individuals, including histological samples, documenting previously unexpected ontogenetic trends and morphological variation in this taxon.