Gyrodactylus jennyae n. sp. is described from the body surface and mouthparts of tadpoles of the bullfrog Rana catesbeiana Shaw imported presumably from Missouri, USA, into a federal government facility in Moncton, New Brunswick, Canada. Its morphology resembles most closely that of G. chologastris Mizelle, Whittaker & McDougal, 1969 described from two amblyopsids (blind cave fishes) in Kentucky and North Carolina. Both species have long slender hamuli, a ventral bar with a relatively long membrane and small anterolateral processes, a cirrus with two rows of small spines and marginal hooks with a well-developed sickle heel and short handle. The two species differ morphologically; G. jennyae has a marginal hook sickle with a more pronounced heel than that found in G. chologastris. A BLAST search using a 945 base pair sequence that included the nuclear ribosomal DNA internal transcribed spacers 1 and 2 and the 5.8S rRNA gene from G. jennyae n. sp. showed that the overall similarity with other Gyrodactylus sequences on GenBank was relatively low. The ITS1 region was similar to that of G. misgurni Ling, 1962; however, no ITS2 and 5.8S rRNA sequences are available for that species. A separate search using 5.8S sequences revealed that G. markakulensis Gvosdev, 1950 and G. laevis Malmberg, 1957 were the closest to G. jennyae (1 and 2 bp differences, respectively). These species are parasites of cyprinids (or their predators) and are similar to G. jennyae and G. chologastris in having a double row of small hooks on the cirrus and overall similar morphologies of the haptoral hard parts. There are now five species of Gyrodactylus described exclusively from amphibians and this appears to have involved at least three separate host-switches from fishes.