Mussel of the

Page last updated
1 June 2023

Mussel of the Month

The January 2004 Mussel of the Month is Alasmidonta heterodon. A. heterodon is one of 70 North American freshwater mussels protected by the U.S. Endangered Species Act.

[We are now going to call this species Prolasmidonta heterodon. — DLG, 1 June 2023.]

Alasmidonta heterodon
ANSP 27341. Philadelphia, Pennsylvania.
[The white scale bar is 2 cm.]

Alasmidonta heterdon (known to those concerned with common names as the dwarf wedgemussel) was once know from at least 70 localities along the eastern coast of North America, from Canada to North Carolina. According to the Recovery Plan (Moser, 1993), it is now limited a few localities in only eight river drainages. There are no longer extant populations in Philadelphia, the locality from which the above figured specimen came.


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily Unionoidea Rafinesque, 1820

Family Unionidae s.s.
Subfamily Unioninae s.s.
Tribe Anodontini Rafinesque, 1820
Subtribe Alasmidontina Swainson, 1840

Genus Alasmidonta Say, 1818

Species Alasmidonta heterodon (Lea, 1829)

For more information about Alasmidonta heterodon, see:
  • Moser, G.A. 1993. Dwarf Wedge Mussel (Alasmidonta heterodon) Recovery Plan. U.S. Fish and Wildlife Service, Region Five, Hadley, MA. 43 pp. + appendix. Available as a pdf from the USFWS.
NSF icon MUSSEL icon
"Making the world a better place, one mollusk at a time."