Résumé
Since two centuries, the fossil record of Elasmobranches (Sharks, Skates and Rays) is mainly constituted by remains of selachians having frequented the shallow waters of the epi-continental seas. As a consequence, very few is known about the fossil selachian communities of the oceanic or bathyal environments. Several paleontological explorations in the paleogene deposits from the South part of the Aquitanian basin led to the discovery of two new fossil selachian associations in the bathyal marls of Landes (South-west of France). These new associations come from two old marl quarries: Tailledis (Saint-Geours-d'Auribat) and Miretrain (Angoume) and are dated to the Ypresian/Lutetian limit and the Middle Lutetian-lower Bartonian respectively. 91 species (68 species of sharks and 23 of batoids belonging to all the modern selachian orders and 68 different genera) are reported here and 73 are illustrated. Among them, only 33 species are already known outside the studied localities. Rest of the fauna consists of new taxa with 29 of them in open nomenclature and 27 described in this work: Orthechinorhinus pfeili, Deania angoumeensis, Scymnodalatias cigalafulgosii, Squaliolus gasconensis, Eosqualiolus aturensis, Acrosqualiolus mirus, Etmopterus cahuzaci, Paraetmopterus nolfi, Pristiophorus lacipidinensis, Orectoloboides reyndersi, Hemiscyllium tailledisensis, Pararhincodon germaini, Woellsteinia kozlovi, Triakis chalossensis, Xystrogaleus cappettai, Apristurus sereti, Scyliorhinus trifolius, Foumtizia poudenxae, Platyrhizoscyllium jaegeri, ?Rhinobatos auribatensis, Raja marandati, Raja michauxi, Hexatrygon senegasi, Coupatezia miretrainensis, Aturobatis aquensis, Torpedo acarinata, Torpedo pessanti. Some of these new species belong to new genera and 7 are described here on their dental morphology: Orthechinorhinus nov. gen. (Squaliformes, Echinorhinidae), Eosqualiolus nov. gen., Acrosqualiolus nov. gen. (Squaliformes, Dalatiidae), Paraetmopterus nov. gen. (Squaliformes, Etmopteridae), Xystrogaleus nov. gen. (Carcharhiniformes, Triakidae); Platyrhizoscyllium nov. gen. (Carcharhiniformes: Scyliorhinidae incertae sedis) and Aturobatis nov. gen. (Myliobatiformes indet.). In addition to the description of these new taxa, analysis on this abundant material allowed: - to review and clarify several attributions, phylogenetic relationships or synonymies for numerous paleogene taxa (e.g. Eosqualiolus, Paraetmopterus, Woellsteinia, Alopias, Orectoloboides, Scyliorhinus, Raja), - to report the first occurrence in the fossil record of some Recent taxa (e.g. Centroscymnus cf. owstoni, the genera Parascyllium, Apristurus, Hexatrygon), - to increase the temporal range of fossil occurrences (e.g. Centrophorus granulosus, Carcharias aff. gracilis, the genera Deania, Squaliolus, Etmopterus, Scymnodalatias, Mitsukurina, Woellsteinia, lago, Orectoloboides), - to enlarge the geographical distributions (e.g. Carcharocles cf. sokolowi, Coupatezia woutersi, Burnhamia daviesi) and to complete the descriptions or the affiliations relating to some paleogene taxa (e.g. Megascyliorhinus cooperi, the genera Isistius, Foumtizia). The most interesting characteristic of these fossil selachian associations is the high proportion of taxa known to inhabit the oceanic and/or bathyal environments, notably the greatest diversity in fossil Squaliformes ever discovered inside a single deposit level (17 species, level 0 of Miretrain) with some taxa commonly observed in more neritic deposits (e.g. Mustelus, Pristiophorus, ?Rhinobatos, Coupatezia) or taxa so far unknown as fossils (Centroscymnus cf. owstoni, the genera Trigonognathus, Parascyllium, Apristurus, Hexatrygon). This systematic study fills in part the considerable gap in our knowledge of the fossil deepwater selachians (especially about the Squaliformes) and provides the evidence that the deep-water selachian communities of the middle Paleogene are as much diversified as the recent ones.