The angled riffleshell, Epioblasma biemarginata, was a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. It is now extinct.This species was endemic to the drainages of the Cumberland River and the Tennessee River in the United States. It was known from several locations in Kentucky, Tennessee, and Alabama. It became extinct due to habitat loss, as the rivers were dammed and diverted.