Reptilian assemblages from the latest Cretaceous – Palaeogene phosphates of Morocco: from Arambourg to present time
Résumé
Arambourg was the first to conduct methodical vertebrate palaeontological studies in the Oulad Abdoun and Ganntour phosphatic basins of Morocco between the 1930s and 1950s. As early as 1935, he identified the main stratigraphical levels of the phosphatic series, characterizing them by a specific association of vertebrates (mainly selachians), and proposed stratigraphical correlations between the phosphatic levels of these two basins. During the last decade, due to a French-Moroccan program of collaboration, vertebrate fossils have been collected in great abundance. Here we present an updated overview of the latest Cretaceous to Ypresian reptilian faunas from the Oulad Abdoun and Ganntour basins, on the basis of published data and new field records. In addition to advances in the study of the already known taxa (i.e., squamates, crocodyliforms, plesiosaurs), recent field works reveal new major reptilian taxa that were unknown (or undescribed) at Arambourg's time: very abundant and diversified marine chelonians (Maastrichtian to Ypresian), scarce dinosaurs and pterosaurs remains (Maastrichtian), and a well diversified marine avifauna (Thanetian and Ypresian). A significant increase in the number of described taxa (52 versus 13) and an improvement of the quality of the specimens found (articulated skeletons versus isolated remains) is worthy of consideration. The Maastrichtian reptilian assemblages are dominated by mosasaurid squamates whereas those of the Palaeogene are by the mirroring crocodyliforms (dyrosaurids and eusuchians).