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 genusMastigodiaptomus—M. maya and M. reidae—are described from material collected in southeastern Mexico. This neotropical genus is known to be distributed mainly in the southern part of the United States, Mexico and Central America, and now embraces 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 that this group of Mexican species represents a northwards radiation from the Proto-Antilles-Central America region into the continent, eventually reaching North America. A key for the identification of the known species of the genus is provided.