Triangle Floater
Alasmidonta undulata
Diagnostics 2
SHELL
- size: small to medium. Maximum 85 mm, but most under 50 mm
- thickness: very thick in anterior, thin in posterior with abrupt mid-shell transition
- shape: oval to ovoid, with posterior more pointed in large individuals. Old, large individuals may have open gap in foot area when shell is fully closed
- width: very inflated,
- surface: smooth
- beaks: elevated and anterior. umbonal cavity deeply set, reaching under pseudocardinals (best viewed facing posterior end) . sculptures: very thick and large single loop bars, the most pronounced of all our native unionids
- color/markings: brownish to greenish with dark green rays throughout. Older shells uniform and very dark.
- sexual dimorphism: none
- pseudocardinal teeth: very strong, often with pronounced serrations ("teeth on teeth"), especially in hard water habitats
- lateral teeth: vestigial. slanted folds radiating from beaks
- nacre: white in posterior, bluish and iridescent in anterior.
Soft parts: foot white or peach
Similar species/lookalikes: usually distinct. The deep umbonal cavity with it's deepest point only visible from a posterior viewpoint is a reliable criteria for quick identification in specimens where the diagnostic extra heavy beak sculptures are dissolved beyond recognition. The pronounced serrations on the pseudo-cardinals is also a telltale feature, when present.
Sources and Credits
- (c) Philippe Blais, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais
- (c) Philippe Blais, some rights reserved (CC BY-SA)
