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. Its natural habitat was shallow, fast moving water of major rivers. It became extinct due to habitat loss, as the rivers were dammed and diverted. The last live individual was seen in 1970.