Quadrula fragosa shell description:

"The shell of the winged mapleleaf is squarish, thick, moderately inflated, and up to 10 cm (4 in.) long. Externally it is brown, and young mussels have faint rays. The shell has a well-developed posterior wing with radiating ridges, and 2 rows of pustules or larger tubercles separated by a sulcus (depression or furrow) extending from the beak to the ventral margin. The pseudocardinal and lateral teeth are well-developed, and the inner shell is white. The winged mapleleaf is very similar to the mapleleaf (Quadrula quadrula), but the wing and 2 rows of pustules or larger tubercles on the winged mapleleaf's shell usually distinguish it from the mapleleaf". (Minnesota Department of Natural Resources).