Since the 1980s, the Upper Jurassic lithographic limestone of the Causse Méjean (southern France) has been known by local naturalists to yield fossils. However, until the beginning of the 21st century, this plattenkalk remained largely undersampled and scientifically underestimated. Here, we present the results of two decades of prospection and sampling in the Drigas and the Nivoliers quarries. We provide the first palaeontological inventory of the fossil flora, the fauna and the ichnofauna for these localities. The fossil assemblages show the co-occurrence of marine and terrestrial organisms. Marine organisms include algae, bivalves, brachiopods, cephalopods (ammonites, belemnites and coleoids such as Trachyteuthis), echinoderms, decapod crustaceans (ghost shrimps, penaeoid shrimps and glypheoid lobsters) and fishes (including several actinopterygians and a coelacanth). Terrestrial organisms consist of plant remains (conifers, bennettitaleans, pteridosperms) and a single rhynchocephalian (Kallimodon cerinensis). Ichnofossils comprise traces of marine invertebrates (e.g. limulid trackways, ammonite touch mark) as well as coprolites and regurgitalites. Given the exquisite preservation of these fossils, the two quarries can be considered as Konservat-Lagerstätten. Both lithological features and fossil content suggest a calm, protected and shallow-marine environment such as a lagoon partially or occasionally open to the sea. Most fossils are allochthonous to parautochthonous and document diverse ecological habitats. Similarly to other famous Upper Jurassic plattenkalks of western Europe such as Solnhofen, Cerin or Canjuers, the Causse Méjean is a key landmark for our understanding of coastal/lagoonal palaeoecosystems during the Kimmeridgian–Tithonian interval.

A recent excavation yielded 118 large tridactyl footprints in the Lower Jurassic Dolomitic Formation of the Causses Basin, at Mongisty in southern France. Most of the tracks are ascribed to Eubrontes giganteus Hitchcock, 1845. They are preserved on a surface of 53 m2 and form parallel rows with a preferential orientation towards the north. Such an abundance and density of E. giganteus is observed for the first time in the Early Jurassic from the Causses Basin. Sedimentological and ichnotaphonomical analyses show that the footprints were made at different time intervals, thus excluding the passage of a large group. In contrast to all other tracksites from the Dolomitic Formation, where tracks are preserved in fine-grained sediments corresponding to low-energy depositional palaeoenvironments, the tracks from Mongisty are preserved in coarse-grained sediment which is a matrix- to clast-supported breccia. Clasts consist of angular to sub-rounded, millimetric to centimetric-scale (up to 2 cm), poorly sorted, randomly oriented, homogeneous dolostone intraclasts floating in a dolomudstone matrix. Sedimentological analysis shows that the depositional environments of Mongisty varied from subtidal to intertidal/supratidal settings in a large and protected flat marsh. The lithology of the track-bearing surfaces indicates that the mudflat of the Causses Basin was sporadically affected by large mud flows that reworked and redeposited mudstone intraclasts coming from the erosion of upstream, dry and partially lithified mud beds. Throughout the world, this type of preservation of dinosaur tracks in tidal matrix- to clast-supported breccias remains rare.