The family comprises 15 species contained in four genera (Macrotrema, Ophisternon,Synbranchus and Monopterus),of which only two,Ophisternon and Synbranchus, with two species in the former genus nd three in the later are currently recognized in the Neotropical region. Synbranchus marmoratus marmoratus, commonly known as the swamp eel or water snake, is widely distributed from Mexico to northern Argentina while Ophisternon aenigmaticum is distributed in Central America:throughout the AtlanticSlope of Guatemala and Mexico to Cuba