Mussel of the

Page last updated
4 September 2007

Mussel of the Month

The September 2007 Mussel of the Month is Pyganodon grandis. Pyganodon is a widespread genus in North America, extenting from the Arctic south to Mexico.

Popenaias popeii
USNM 86381. Lake Champlain, Vermont.
(paratype of Symphynota benedictensis Lea)

Pyganodon grandis is hands down the most widely distributed freshwater mussel in North America. The species is known from Arctic Canada to Mexico, its range occupying much of the region east of the Rocky Mountains. No mussel gets that far being a specialist, and P. grandis is found in various habitats (from lake to large rivers) and on many different host fish. As a result, it is an extremely variable mollusk, and the current taxonomy of P. grandis incorporates numerous described forms.

Until recently (the last quarter of the 20th century), Pyganodon was lumped into the widespread, European genus Anodonta. However, the phylogenetic evidence to-date suggests that Pyganodon is more closely related to other North American anodontines than to any Old World taxa.


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily UNIONOIDEA Rafinesque, 1820

Family UNIONIDAE s.s.
Subfamily UNIONINAE s.s.
Tribe ANODONTINI Rafinesque, 1820

Genus Pyganodon Crosse & Fischer, 1894

Species Pyganodon grandis (Say, 1829)

For more information about Pyganodon, check out:
  • Cummings, K.S. & C.A. Mayer. 1992.Field guide to freshwater mussels of the Midwest. Illinois Natural History Survey Manual 5. 194 pp.
  • Parmalee, P.W. & A.E. Bogan. 1998. The freshwater mussels of Tennessee. University of Tennessee Press, Knoxville 328 pp.
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