Ptychobranchus fasciolaris



  • size: mid-sized to large
  • thickness: thick
  • shape: elliptical to arched dorsally, bluntly pointed in posterior, rounded in anterior. ventral margin nearly straight to concave in older animals
  • width: moderately compressed
  • surface: smooth
  • beaks: lightly elevated above hinge line. sculptures: several indistinct wavy ridges.
  • color/markings: yellow or tan to dark brown in older adults. Interrupted, tightly packed groups of narrow green rays in youngest part of periostracum.
  • sexual dimorphism: subtle. mature females with a more pronounced radial groove in posterior inner shell
  • pseudocardinal teeth: moderately thick , serrated
  • lateral teeth: strong. lower left valve tooth very thick, shorter than upper tooth, and protruding down into cavity
  • nacre: white

Soft parts: foot white. mantle dark, very long and narrow inhalant siphon with very short and dense papillae.

Similar species/lookalikes: Live young adults and and juveniles easily identified by the unique green ray pattern of a pale yellow background and elliptical shape. Older, more elongate adults with obscured rays can be confused with equally old spikes, Eurynia dilatata. On average most E. dilatata are more elongate and kidneyshells are more compact, but extremes in shell shape variations in both taxons might produce individuals of very similar shape. Fresh shells are also usually quite distinctive, as combination of wide, interrupted green rays, white nacre and shorter lower lateral tooth in left valve is diagnostic. However, weathered valves of adults of those two species might be extremely difficult to tell apart if beak sculptures, periostracum raying and nacre color become obscured or lost, for the inner shell features are virtually identical (our only two native species with a shorter lower left valve lateral tooth protruding down into cavity)


Lake Huron-St-Clair dr.:

  • Ausable R.
  • Maitland R.
  • Sydenham R.
  • Thames R.
    Lake Erie dr.:

  • Grand R.

Sources and Credits

  1. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais,
  2. (c) wesleyhoup46, some rights reserved (CC BY-NC),
  3. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais,
  4. (c) Matthew Ireland, some rights reserved (CC BY-NC),
  5. (c) Pat Deacon, some rights reserved (CC BY-NC),
  6. (c) Evan Raskin, some rights reserved (CC BY-NC),
  7. Adapted by Philippe Blais from a work by (c) Wikipedia, some rights reserved (CC BY-SA),
  8. (c) Philippe Blais, some rights reserved (CC BY-SA)

More Info

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