Fragile Papershell
Potamilus fragilis
Diagnostics 2
SHELL
- size: large. maximum 185mm, most under 100 mm
- thickness: thin, brittle
- shape: oval to elliptical, usually with distinct wing on posterior slope that can vary from pronounced to almost absent, more obvious on young.
- width: moderately to very compressed
- surface:smooth when young, relatively roughened with growth rings with age.
- beaks: slightly elevated. sculptures: faint ridges radiating from beak apex mainly in posterior, usually prematurely dissolved/eroded, especially in anterior, even in very young individuals.
- color/markings: straw yellow to tan, darker in old adults. occasional faint green rays
- sexual dimorphism: can be subtle, but usually clearly obvious: females with marsupial margin more rounded, giving a rear-heavy look. males have an overall even oval shape except for dorsal wing. Males grow much larger than females.
- pseudocardinal teeth: rudimentary to nearly absent (especially in left valve), flattened, weakly protruding into beak cavity from hinge line
- lateral teeth: thin but well defined
- nacre: iridescent, white, with pink flush close to hinge, predominantly near lateral teeth
Soft parts: foot white. apertures wide, yellow with darker inner and outer marblings on exhalent aperture. inhalant aperture with unforked papillae with pale tips/inner side, contrasting with darker base on out facing side and interstices. (very similar to Lampsilis cardium aperture criteria)
Similar species/lookalikes: usually distinct. weathered shell specimens can become much darker and resemble very weathered shells of Potamilus alatus, but in this taxon pseudocardinals protrude clearly from hinge line into cavity. broken/weathered shells can resemble Lampsilis cardium, but that species is clearly more inflated, even when very young, and if often rayed.
Combination of pale yellow color, very compressed, thin shell and dorsal wing (when present) is 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/Leptodea_fragilis
