Résumé
The Early-Late Cretaceous transition (Late Albian-Early Cenomanian; ~100 Ma) witnessed marked environmental changes and a deep reorganization of the marine fauna. Nevertheless, the impact of these environmental and biotic changes on Eurasian marine vertebrates remains poorly understood, as specimens from this area are mostly represented by fragmentary and isolated remains occurring in reworked, bonebed-like deposits. Here we report vertebrate remains from an upper Albian marine fossiliferous bed from the Geological Reserve of Digne (Alpes-de Haute-Provence, southeastern France), recovered with diverse invertebrate species (ammonoids, belemnoids, brachiopods and inoceramid bivalves). The fossiliferous bed consists of glauconitic marls enriched in planktic foraminifera and occurs within an expanded and monotonous succession of micaceous marls interbedded with silty carbonate levels that were deposited in the pelagic domain of the SE French Basin. The ammonite fauna is quite exceptional by its abundance, diversity and quality of preservation (i.e., large specimens preserving very fragile shell features that are generally not fossilized) and indicate that the investigated bed belong to the Mortoniceras fallax ammonite Biozone (Middle-Late Albian). The diverse vertebrate fauna consists of chondrichthyans, ichthyosaurs and plesiosaurs. Chondrichthyans are represented by five shark species belonging to the order Lamniformes. This shark assemblage is dominated by Sphenodus teeth and comprises predator taxa probably living in temperate waters and indicative of open marine settings. The site yielded a large, partial post-cranial plesiosaur skeleton with articulated elements probably belonging to an elasmosaurid (long necked) taxa and representing one of the most complete Albian plesiosaur specimen known from Europe. These findings indicate that this new paleontological site holds promising clues about the evolutionary history of major groups of marine vertebrates near the Early-Late Cretaceous transition.