Bony fishes from the Sinemurian (Jurassic) Osteno Konservat-Lagerstätte (Como, NW Italy)

Located in the Lombardy Basin of Northern Italy, the Osteno Konservat-Lagerstätte preserves an exceptionally diverse Lower Jurassic marine assemblage that, despite yielding extraordinary amounts of data over the past 60 years due to the remarkable preservation of its specimens, has long had its vertebrate component largely overlooked. This study presents a detailed morphological and taxonomic analysis of the bony 􀃀sh fauna recovered from this unique deposit. Seven distinct taxa have been identi􀃀ed, four of which are shared with the renowned Lyme Regis Lagerstätte (Dorset, UK): Holophagus cf. gulo, Dapedium sp., Furo sp., and Dorsetichthys bechei, a unique stem teleost whose occurrence at Osteno further strengthens the possibility of faunal contact between English and northern Italian Sinemurian communities. Three novelties characterize the Osteno ichthyofauna: Ostenolepis marianii gen. n. sp. n., a small palaeoniscimorph with 􀃀nely ornamented scales; Peripeltopleurus jurassicus sp. n., the last representative of the Peltopleuriformes, an order previously restricted to the Middle and Upper Triassic; and Pholidolepis teruzzii sp. n., a stem-teleost related to Pholidolepis dorsentensis from Lyme Regis, but lacking any scale covering. The discovery of these taxa signi􀃀cantly contributes to our understanding of Sinemurian ichthyofaunas while shedding new light on the paleoenvironmental dynamics along the northwestern margin of the Neotethys. Overall, this study underscores the critical importance of the Osteno site for reconstructing patterns of diversity and biogeographic connectivity during a pivotal interval in vertebrate evolution