New York Natural Heritage Program
Dwarf Wedgemussel
Alasmidonta heterodon (I. Lea, 1830)
Bivalves

New York State Distribution [-]
The only two known populations occur in the upper Delaware River in Sullivan and Delaware Counties and one of its major downstream tributaries, the lower Neversink River in Orange County.

Global Distribution [-]
Today dwarf wedgemussels are discontinuously distributed along Atlantic seaboard drainages from New Hampshire to North Carolina (New Hampshire, Vermont, Connecticut, New York, New Jersey, Pennsylvania, Massachusetts, Maryland, Virginia, North Carolina), but in 1999 it was declared extirpated from New Brunswick. The dwarf wedgemussel was first described from the Schuylkill River in Pennsylvania although it has not been seen in that river since 1919. Historically known from about 70 locations in 15 major drainages, it was listed as a federally endangered species in the United States in 1990. When the federal recovery plan was published three years later, the dwarf wedgemussel was known to exist in only 20 of 70 locations where it had originally been known to occur. Most of the populations were thought to be small and declining. Since the federal recovery plan was published in 1993, surveyors have found nearly 40 new populations in locations where the species had been presumed extirpated or in rivers where the species had never been found (Nedeau 2005).
Best Places to See
• Neversink River (Orange County)