Two new Mastigodiaptomus (Copepoda, Diaptomidae) from southeastern Mexico,with a key for the identification of the known species of the genus

Two new species of the freshwater planktonic copepod genus Mastigodiaptomus -M. maya and M. reidae-are described from material collected in southeaster n Mexico. This neotropical genus is known to be distributed mainly in the s outhern part of the United States, Mexico and Central America, and now embr aces eight species. Of these, six occur in Mexico. Both new species seem to be closely related to M. texensis and M. albuquerquensis. It is probable t hat this group of Mexican species represents a northwards radiation from th e Proto-Antilles-Central America region into the continent, eventually reac hing North America. A key for the identification of the known species of th e genus is provided.