Paper Pondshell
Utterbackia imbecillis
Diagnostics 4
SHELL
- size: mid-sized. maximum 90 mm. most under 70 mm
- thickness: thin to very thin and brittle
- shape: oval-elongate, commonly coffin-shaped with pointed posterior end. posterior ridge weak, often double, often curved dorsally towards posterior end in adults. weak dorsal wing common. hinge line typically very straight.
- width: very compressed in young to very inflated, nearly cylindrical in older adults
- surface: smooth, often shiny
- beaks: flat, even with hinge line (best viewed from inside of shell). sculptures: Two types of intermingled ridges. short, more pronounced, truncated double loop ridges, inlaid within more numerous, finer, complete, single loop ones that extend well beyond the former. Thus forming an overall muddled, irregular pattern. Very small mucro (nub) common at umbonal apex.
- color/markings: yellowish green to pale green, commonly with faint green rays on disk, with 2 wider green rays on posterior ridges.
- sexual dimorphism: none
- pseudocardinal teeth: absent
- lateral teeth: absent
- nacre: bluish-white, irridescent
Soft parts: foot white
Similar species/lookalikes: size, shape and color very similar with Eastern floater and young individuals of giant floater, but those taxons have clearly elevated beaks above hinge line and sculptures much more clearly defined when present, and can grow much larger. Shell usually also thicker than paper pondshell, but that character can vary according to water hardness of habitat for both species. Beak sculptures, when present, very different for those two taxons. In Canada, flat beaks flush with hinge line is diagnostic on it's own for this taxon.
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
- (c) Chuck Sexton, some rights reserved (CC BY-NC), uploaded by Chuck Sexton
- Adapted by Philippe Blais from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Utterbackia_imbecillis
