Truncilla truncata



  • size: small to mid-sized, maximum 95 mm; most specimens under 60 mm
  • thickness: moderately thick to thick
  • shape: triangular or drop shaped. posterior slope sharply angled from posterior ridge, giving a truncated appearance, posterior end pointed, often amplified by adjacent slight sulcus.
  • width: very inflated
  • surface: smooth
  • beaks: very elevated, curved inward. sculptures: few fine double loop ridges
  • color/markings: highly variable: periostracum pale yellow or brown to greenish or even reddish; sparse to crowded green rays of various width overlaid with darker chevrons, dashes, wavy lines or blotches; concentric bands of differing patterns along growth lines are common.
  • sexual dimorphism: subtle to none
  • pseudocardinal teeth: strong, serrated, anterior tooth of left valve long and curved dorsally
  • lateral teeth: well defined
  • nacre: white, occasionally pink

Soft parts: creamy white

Similar species/lookalikes: Most adults usually readily identifiable from the distinctive teardrop shape and sharp posterior ridge. But young specimens may also resemble Snuffbox, Epioblasma triquetra, but that species usually has sharply defined triangular markings pointing downwards, away from beaks. Young specimens can look very similar to adult T. donaciformis, especially large males, in which sharpness of posterior ridge may be similarly pronounced. Color and patterning can be confusingly similar in both species. T. donaciformis has more centrally located, less inflated beaks, and a posterior ridge that is less sharp. Pink nacred variants are not known for T. donaciformis.

A helpful feature to discern the two at any age is the wide angle formed by anterior slope of beaks where it meets the upper edge of the anterior hinge upon lateral viewing: angle is SHARP in T. truncata, whereas SMOOTH/BLUNTED in T. donaciformis .



  • Ausable R.
  • Sydenham R.
  • Ruscom R.
  • Thames R. < Baptiste Cr.
  • Grand R.

Sources and Credits

  1. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais,
  2. (c) Matthew Ireland, some rights reserved (CC BY-NC),
  3. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais,
  4. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais,
  5. (c) Peg Furshong, some rights reserved (CC BY-NC),
  6. (c) Peg Furshong, 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)

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