Northern Riffleshell
Epioblasma torulosa rangiana
Diagnostics 2
SHELL
- size: small
- thickness: thick in anterior; very thin and brittle towards posterior in adult females
- shape: quadrate in males and very young females, oval or egg-shaped in adult females
- width: inflated
- surface: smooth, with irregularities along growth lines on posterior half
- beaks: swollen above hinge line; sculptures few, weak single loops
- color/markings: yellowish to pale brown with crowded, thin green rays
- sexual dimorphism: pronounced: males attain much larger size and retain wide sulcus below posterior ridge throughout life, whereas in females is is filled and swollen to form a rounded and irregular extension in marsupial area; edges of shell in that area lined with minute teeth angled inward
- pseudocardinal teeth: strong , one in right valve, two in left.
- lateral teeth: strong, lower of left valve thickened
- nacre: white
Soft parts: White; mantle lure display in females: smooth, bright white and wide 'curtains'
Similar species/lookalikes: distinctive. males resemble deertoe in shape, but that species usually has very different and elaborate raying /markings and sulcus is much less pronounced and narrower when present, and posterior ridge is much sharper and beaks are higher above hinge line. The marsupial area shell swelling in adult females is very distinctive among Canadian unionids, and therefore diagnostic.
Sources and Credits
- (c) Philippe Blais, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais
- Adapted by Philippe Blais from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Epioblasma_torulosa_rangiana
