Mussel of the

Page last updated
11 December 2017

Mussel of the Month

The December 2017 Mussel of the Month is Elliptio crassidens. Elliptio is a genus of 30 species found in eastern North America.

ANSP 20243. River Ohio (Poulson "type" of U nigra).

For more than a decade, we have been working our way through the freshwater mussel genera. We thought that we had handled this particular widespread Nearctic genus way back in November 2003 when we shined the spotlight on Elliptio dilatata (the 4th Mussel of the Month ever!). But, the shifting sands of freshwater mussel taxonomy have revealed a new genus-level classification. That species now belongs to the genus Eurynia.

We have had a haboob of genus- and species-level revisions to the MUSSELp Database in recent months. There have been several important publications of late, but the big one for North American mussels is been Williams et al. (2017) — the modern update of Williams et al. (1993) and Turgeon et al. (1998). We will use upcoming Mussel of the Month posts to roll out other such revisions for Europe and Southeast Asia.

E. dilatata was removed from Elliptio because it is never recovered in phylogenetic analyses as a part of the Elliptio clade (Campbell et al., 2005, 2012; Pfeiffer et al., 2016; Perkins et al., 2017). In addition to various generic shuffles, 13 new species of North American mussels were added to our list and 13 more were synonymized away. This momentary confusion is progress! We now report a world-wide total of 906 Recent species of freshwater mussels of the Order Unionoida — exactly one-third of which are found in North America.

These changes have been incorporated into this web site in two places. We have updated the MUSSEL Project Database. The MUSSELpdb is comprehensive and searchable. We have also reviewed, refined, and reformatted the static Unionoida cum Grano Salis pages, which summarize taxonomic and geographical diversity — the frequently updated version of our global checklist (Graf & Cummings, 2007).


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Family UNIONINDAE Rafinesque, 1820
Subfamily AMBLEMINAE Rafinesque, 1820
Tribe PLEUROBEMINI Hannibal, 1912

Genus Elliptio Rafinesque, 1819

Species Elliptio crassidens (Lamarck, 1819)
(+ E. nigra Rafinesque)

To find out more about Elliptio crassidens and the classifcation of North American freshwater mussels, check out:
NSF icon MUSSEL icon
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