Acolpenteron willifordensis n. sp. (Monogenoidea: Dactylogyridae) is described from the ureters and kidney (presumably the renal tubules) of the spotted sucker Minytrema melanops (Cypriniformes: Catostomidae) collected from the Econfina Creek in the panhandle of northern Florida. The new species is similar to Acolpenteron catostomi Fischthal and Allison, 1942 in body shape and size, position of the vaginal pore, and the general shape of the posteriorly notched haptor. It differs from A. catostomi by having a broad tubular shaft of the male copulatory organ that lacks a proximal double recurve immediately distal to its base. Possible biogeographic explanations for the occurrences of species of Acolpenteron in primary freshwater fishes of North America, Eurasia and South America are presented.