Creeper
Strophitus undulatus
Diagnostics 3
SHELL
- size: medium sized. maximum 110 mm, but most under 70 mm
- thickness: thin to medium thickness
- shape: very variable, even within the same locality. Oval to triangular , wedge-shaped in cross-section as older adults, usually well defined downward dip of hinge line right in front of beaks, more obvious on inner shell, but often obvious in live animals as well, especially older ones. This feature can be quite subtle or absent, however. adults with a more compact shape often display a 'hunched forward' appearance.
- width: moderately compressed to very inflated
- surface: smooth
- beak: well elevated from hinge line. sculptures: well defined single loop bars with a sharp angle anteriorly. many fine radiating ridges near ligament in front. Single loops sharply angled toward hinge line in front. but more pronounced, more angular, and overall larger in creeper. Also note first loops in cylindrical papershell are 90 degrees angled from hinge line in front, but closer to 45 degrees in creeper.
- color/markings: pale brown with numerous fine green rays mostly in the back, becoming very dark brown and uniform with age
- sexual dimorphism: none
- pseudocardinal teeth: none to rudimentary knobs, rarely more pronounced and lamellar
- lateral teeth: none. Rounded thickening of hinge line
- nacre: bluish white with a salmon flush in the beak cavity
Soft parts: foot beige to light orange
Similar species/lookalikes: The Great Imitator! Of all our Canadian natives, this taxon is probably the most likely to be confused with another , as it is found in many different habitats, cohabiting with many other species throughout its range. very variable species, much influenced by water flow and water hardness of habitat. Young specimens often particularly hard to differentiate from cylindrical papershell, Anodontoides ferussacianus that is frequently sympatric. Compared to that species beak sculptures show same pattern of single loops sharply angled toward hinge line in front of beaks, but more pronounced, , more angular, and overall larger in creeper. Also first loops in cylindrical papershell are roughly 90 degrees angled from hinge line in front, but closer to 45 degrees in creeper. As sculptures are often dissolved/eroded, the dip of the hinge line in front of the beaks then becomes the easiest way to differentiate from that species, as all other shell characters (even foot color!) can be very similar. See pictures for subtle differences in beak sculptures. Live specimens with atypical shell shapes may resemble young Pyganodons, Eastern elliptios or Spike. Some specimens with a more abrupt posterior slope may also resemble spotless elktoes, with which their share common traits concerning variable vestigial pseudocardinals, shell shape and foot color. The elktoes' posterior slope's fine ribbing is then key to differentiation.
Sources and Credits
- (c) Philippe Blais, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais
- (c) Matthew Ireland, all rights reserved, uploaded by Matthew Ireland
- Adapted by Philippe Blais from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Strophitus_undulatus
