About Pyganodon grandis (Say, 1829)
Pyganodon grandis, commonly called the giant floater, is a species of freshwater mussel. It is an aquatic bivalve mollusk that belongs to Unionidae, the family of river mussels. This species is characterized by fast growth, a large adult size, and a short lifespan. It is highly morphologically variable and has a widespread distribution across the United States and southeastern Canada. The original 1829 species description by Say reads: "Shell very large, subovate; disk unequally wrinkled and undulated transversely, dark yellowish brown; umbo elevated; beak slightly elevated, with generally, two or three small sinuous, acute undulations; hinge margin slightly arquated, sometimes nearly rectilinear, somewhat angulated at its anterior termination, thence the edge descends by a nearly rectilinear, or slightly concave line to the anterior margin, which is considerably narrowed; sinus of the hinge margin concave; posterior margin widely rounded; within white margined, particularly before, with dusky."
