In marine and freshwater teleosts, they live as parasites inside the digestive tract, especially the intestine.

[4] The genus Bucephalus was based on the earliest known bucephalid, B. polymorphus Baer (1827), initially described from a cercaria larva.

'ox head') was chosen because of the horn-like appearance of the forked tail (furcae) of its cercaria.

By what Manter calls a "curious circumstance", horns are also suggested by the long tentacles of adult worms.

[4] An earlier name for this genus was Gasterostomum, given by von Siebold in 1848 to all adult trematodes with a ventral mouth.