Mid-Cretaceous terrestrial biota from Charentes, SW France: a synthesis of 10 years of investigations

Since the discovery in summer 1999 of the first animal inclusions in amber, the Albian -Cenomanian deposits of the Charentes region (SW France) have yielded rich and diverse assemblages of continental organisms. Four major groups have been studied in detail: (1) plants, (2) arthropods in amber (3) microorganisms in amber, and (4) vertebrates. Main palaeobotanical discoveries come from two quarries in the localities of Archingeay-Les Nouillers, where exceptionally preserved leaf cuticles have been found, and Puy-Puy, at Tonnay-Charente, which is especially rich in angiosperm impressions (more than 20 species identified). Three Uppermost Albian and six Lowermost Cenomanian sites have produced large amounts of amber, from which numerous insects and other arthropods have been described, such as various primitive ants or the oldest mole cricket and mecysmaucheniid spider. In association to the arthropods, Charentes amber provides infrequent inclusions such as reptile skin, dinosaur feathers and mammal hairs, or marine plankton including diatoms, dinoflagellate cysts, foraminifers or larval echinoderm spines. Charentes amber is generally dark and opaque and the use of Synchrotron imaging allows 3D reconstruction of arthropods that could not be observed by classic optical methods. Finally, most of the Cenomanian paralic deposits that contain plant fossils and amber have also yielded rich microassemblages of vertebrates, among which numerous fish and selacian teeth as well as remains of dinosaurs (carcharodontosaurids, troodontids, iguanodontids, ...), pterosaurs (ornitocheirids) and marsupial (?) mammals. The exceptional richness and diversity of these deposits allow for interpretation of the mid- Cretaceous terrestrial palaeoenvironment of Charentes as a coastal forest dominated by Araucariaceae and Cheirolepidiaceae, while angiosperms become more abundant toward the continent, in an insular context favourable to endemism and vertebrate dwarfism.