Early Paleozoic echinoderms from Montagne Noire: biostratigraphy and palaeodiversity

Early Palaeozoic echinoderm faunas from Montagne Noire represent some of th e richest and most diversified assemblages known so far. This situation res ults from their interest and from more than one century of active research. Study of echinoderms and associated faunas allows us to place them in a we ll-defined regional stratigraphical framework extending from the Middle Cam brian up to the Arenig, and to illustrate the influence of palaeoenvironnen ts in the distribution and diversity of echinoderms. Montagne Noire faunas show strong affinities with other assemblages from the northern margin of G ondwana (palaeogeographical implications). Variations in the biodiversity o f Cambro-Ordovician echinoderms from Montagne Noire indicate that the radia tion observed at the base of the Ordovician may result, at least partly, fr om a too imperfect knowledge of Upper Cambrian faunas.