Eastern Floater

Pyganodon cataracta

DIAGNOSTICS 8

SHELL

  • size: mid-sized to large, maximum 150 mm. most specimens under 100 mm
  • thickness: thin, fragile
  • shape: elliptical, often shoe-shaped. posterior ridge faint but distinct, often slight dorsal curve towards posterior end in mature adults.
  • width: moderately to very inflated
  • surface: smooth, often shiny
  • beaks: slightly elevated above hinge line, inflated, located in anterior third or quarter of shell. sculptures: often partially or completely dissolved/eroded in most specimens, but often also discernible from inside of shell. 6-8 double even spaced looped bars of even height (not nodulous). first loops sometimes interrupted in inter-loop notch. middle bars width about equal with bar spacing.
  • color/markings: greenish-yellow or yellow-tan to brown. faint green rays common in young, mostly in posterior part of shell
  • sexual dimorphism: none
  • pseudocardinal teeth: none
  • lateral teeth: none
  • nacre: bluish white, irridescent

Soft parts: foot beige to orangish

Similar species/lookalikes: easily confused with the extremely variable giant floater Pyganodon grandis in particular, which can take on the same elongate-elliptical shape and has very variable sculptures as well. The ''even-even" criteria regarding beak sculptures seems most helpful, in contrast to the "uneven-uneven" sculptures of P. grandis. Most P. grandis have a much curvier ventral edge, and are overall more stocky, with more central beaks. very similar to paper pondshell, but that taxon is usually thinner-shelled, has flat beaks that are even with hinge line, and very different beak sculptures. It could also possibly be confused with the Newfoundland floater Pyganodon fragilis and lake floater Pyganodon lacustris. these two taxons can be extremely similar in most characters and sculptures . Also, this last and most useful identification criteria is often too degraded by dissolution or erosion to be reliable in the majority of specimens. Reliable data about sculpture variations in all these species is currently sorely lacking or hard to find. Whats more, the occurrence of hybrids is possible, further complicating reliable identification without genetic testing. IMPORTANT NOTE: taxonomy of the genus Pyganodon, especially concerning P. lacustris, is still currently not definitive, awaiting further genetic studies.

Sources and Credits

  1. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais, https://www.inaturalist.org/photos/12696684
  2. (c) Jason Hill, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais, https://www.inaturalist.org/photos/12816281
  3. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais, https://www.inaturalist.org/photos/73908634
  4. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais, https://www.inaturalist.org/photos/73908639
  5. (c) redgarter, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais, https://www.inaturalist.org/photos/73908629
  6. (c) Philippe Blais, some rights reserved (CC BY-NC-ND), https://www.inaturalist.org/photos/10165550
  7. (c) Jason Hill, some rights reserved (CC BY-NC-ND), uploaded by Philippe Blais, https://www.inaturalist.org/photos/12816282
  8. (c) Philippe Blais, some rights reserved (CC BY-SA)

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