The collection of four specimens of Glyphobothrium zwerneri extends the geographic distribution of the species from the original locality (Chesapeake Bay, Virginia, U.S.A.) to at least Ciudad del Carmen, Campeche, México, at the southern limit of the Gulf of Mexico. The species is a parasite of Rhinoptera bonasus, a stingray that is thought to migrate within a wide range, suggesting that conservation efforts should be consistent within the stingray’s range, just as is necessary for birds and other species that migrate.