Pyganodon grandis
Conservation status
Least Concern (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Unionida
Family:	Unionidae
Genus:	Pyganodon
Species:	P. grandis
Binomial name
Pyganodon grandis (Say, 1829)
Synonyms[2]
List Anodonta grandis Say, 1829 Anodonta grandis subsp. grandis Say, 1829 Anodonta grandis subsp. simpsoniana Lea, 1861 Anodonta grandis subsp. corpulenta Cooper, 1834 Anodonta lugubris Say, 1829 Anodonta inflata Rafinesque, 1831 Anodonta stewartiana Lea, 1834 Symphynota benedictensis Lea, 1834 Anodonta corpulenta Cooper, 1834 Anodonta plana Lea, 1834 Anodonta declivis Conrad, 1834 Anodonta gigantea Lea, 1838 Anodonta ovata Lea, 1838 Anodonta salmonia Lea, 1838 Anodonta decora Lea, 1838 Anodonta pepinianus Lea, 1838 Anodonta harpethensis Lea, 1840 Anodonta footiana Lea, 1840 Anodonta maryattana Lea, 1840 Anodonta globosa Lea, 1841 Anodonta virens Lea, 1852 Anodonta linnaeana Lea, 1852 Anodonta opaca Lea, 1852 Anodonta lewisii Lea, 1857 Anodonta danielsii Lea, 1858 Anodonta gesnerii Lea, 1858 Anodonta texasensis Lea, 1859 Anodonta kennicottii Lea, 1861 Anodonta simpsoniana Lea, 1861 Anodonta leonensis Lea, 1862 Anodonta dallasiana Lea, 1863 Anodonta bealei Lea, 1863 Anodon subangulata J.G. Anthony, 1865 Anodon subinflata J.G. Anthony, 1865 Anodon imbricata J.G. Anthony, 1865 Anodon micans J.G. Anthony, 1865 Anodon opalina J.G. Anthony, 1865 Anodon mcnielii J.G. Anthony, 1866 Anodon subgibbosa J.G. Anthony, 1866 Anodon inornata J.G. Anthony, 1866 Anodon nopalatensis Sowerby, 1867 Margaron benedictii Lea, 1870 Anodonta sulcata Küster, 1873 Anodonta somersii Call, 1880 Anodonta houghtonensis Currier in DeCamp, 1881 Anodonta grijalvae Morelet, 1884 Anodonta tabascensis Morelet, 1884 Anodonta dakota Frierson, 1910 Anodonta dakotana Utterback, 1915 Anodonta inflata subsp. viridis Rafinesque, 1831 Anodonta inflata subsp. fuscata Rafinesque, 1831 Anodonta inflata subsp. zonalis Rafinesque, 1831

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Pyganodon grandis, the giant floater, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. This species is fast-growing, large, and has a short lifespan. It is variable and widespread^[3] across the United States and southeastern Canada.

Original description (Say 1829): "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."