The nomenclature and taxonomic revision presented in this article addresses the genus Marsilea L. in Madagascar. It supplements and amends the last revision from Launert (1984) and the last synthesis from Roux (2009). This new treatment provides:
1) an original identification key;
2) the description and illustration of two new species: Marsilea globulosa I.Bouchart, sp. nov. whose sporocarp is globular, small in size with a highly acute and acuminate upper tooth, and Marsilea pyriformis I.Bouchart, sp. nov. whose sporocarp is pyriform with a very long, acute, and often strongly curved tooth at mid-length;
3) lectotypifications for Marsilea muscoides Lepr. ex. A.Braun, Marsilea trichopoda Lepr. ex. A.Braun, Marsilea diffusa Lepr. ex. A.Braun f. madagascarensis and Marsilea diffusa Lepr. ex A.Braun var. cornuta A.Braun ex Kuhn;
4) the first record in Madagascar of an African species: Marsilea macrocarpa C.Presl;
5) description and illustration of the five other Malagasy Marsilea species.
These taxonomic and nomenclatural modifications increase the number of Marsilea species present in Madagascar to seven. Two of them are endemic.
Marsileaceae, Madagascar, original identification key, lectotypifications, new record, new species