Dwarf Wedgemussel

Alasmidonta heterodon

Diagnostics 2


  • size: small. maximum 50 mm, most specimens under 40 mm
  • thickness: thin
  • shape: trapazoidal with pointed posterior end, rounded of straight posterior slope
  • width: medium inflated
  • surface: smooth
  • beaks: slightly elevated. sculptures: 4 curved ridges angular towards posterior slope
  • color/markings: periostracum yellowish brown to brown. greenish rays in young
  • sexual dimorphism: female shells more inflated posteriorly
  • pseudocardinal teeth: small, compressed
  • lateral teeth: well developed, with TWO IN RIGHT VALVE AND ONE IN LEFT valve in most specimens
  • nacre: white to bluish


SIMILAR SPECIES/LOOKALIKES: the small size and very restricted geographical range make this rare species easy to identify. The aberrant/reversed lateral tooth arrangement on its own is diagnostic when present. IMPORTANT NOTE: this species is considered extirpated/extinct at this point in Canada, as it hasn't been found since 1968.

Sources and Credits

  1. A.E. Bogan, J. Alderman, and J. Price, no known copyright restrictions (public domain), http://commons.wikimedia.org/wiki/File:Alasmidonta_heterodon.jpg
  2. Adapted by Philippe Blais from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Alasmidonta_heterodon

More Info

iNatCA Map