Un nouveau Microcharon (Isopoda, Janiroidea) du Maroc — origine et biogéographie historique

The interstitial crustacean isopods of the genus Microcharon (Microparasellidae) are relatively well-diversified and widely distributed in Morocco. A new species, M. boutini, is described. The 5-dentate mandibular pars incisiva, the elongated inner lobe of the exopodite, and the reduced armature of the first male pleopod characterize the species. M. boutini n. sp. belongs to the monophyletic messoulii group of species, the most primitive representatives of the genus. The distribution of M. boutini n. sp. covers both the northwestern part of the Jbilet and the nearest adjacent plain, as well as the High Atlas of the Marrakech piedmont. From a historical biogeographic point of view, interstitial ancestral marine populations would have been left in subterranean continental waters by the regression of the “Phosphate Sea” during the Lutetian (Eocene). The distribution of the same species both in High Atlas valleys and in the Jbilet region poses an evolutionary rate problem.