Page last updated
8 August 2018

Unionoida cum Grano Salis

Introduction

One of the objectives of the MUSSEL Project is to document the global diversity of freshwater mussels. Towards this end, we have developed the MUSSEL Project Database to manage the various nomenclatural, phylogenetic and specimen-based information on the Unionoida. Unionoida cum Grano Salis ("freshwater mussels with a grain of salt") is our attempt to pull together what is currently known of the worldwide, species-level diversity of these freshwater mollusks. Background information about our broader goals can be found on this web site, including our database model and our related publications. These Unionoida cum Grano Salis pages document our current estimate of global freshwater mussel diversity, report how it is partitioned both taxonomically and geographically and list all currently recognized taxa. These data and conclusions must be taken with a grain of salt, as many taxa have not been reevaluated using modern methods. Overall, we suspect that the known global diversity of freshwater mussels (as presented here) is an underestimate.

Previous Estimates: Simpson and Haas

We are not the first to describe the diversity of the Unionoida. However, the only previous (published) global assessments of species-level diversity were undertaken by Charles T. Simpson at the turn of the 20th century and Fritz Haas in 1969.

• Simpson, C.T. 1900. Synopsis of the naiades, or pearly fresh-water mussels. Proceedings of the United States National Museum 22(1205): 501-1044.
• Simpson, C.T. 1914. A descriptive catalogue of the naiades, or pearly fresh-water mussels. Parts I-III. Bryant Walker, Detroit, Michigan.
• Haas, F. 1969. Superfamilia Unionacea. Das Tierreich (Berlin) 88.

Simpson, working on behalf of Isaac Lea's heirs, created a cosmopolitan synopsis of the Unionoida, reducing the more than 4000 available freshwater mussel names of the 19th century to about 1300 valid species. Haas took that effort even further and was able to bring the total down to just over 830 species. The described taxa dealt with my Simpson and Haas are available on this web site in the MUSSEL Project Database.

Our Estimate of Global Diversity

Our estimate of global diversity is based upon the comprehensive MUSSELp Database. The data presented here were taken from the literature, and this is an on-going process. This work is best considered a review rather than a revision. The published version of Unionoida cum Grano Salis provides a broader discussion, a comprehensive bibliography, and a checklist of all species of freshwater mussels recognized at the time that article went to press.

• Graf, D.L. & K.S. Cummings. 2007. Review of the systematics and global diversity of freshwater mussel species (Bivalvia: Unionoida). Journal of Molluscan Studies 73: 291-314.

We have continued to update our species list and estimates of diversity as our research has progressed. Moreover, the MUSSEL Project Web Site allows us to integrate this work with other projects. This will allow us to keep these data current and facilitate the use of our web site as a research tool.

• The first such major update was done on 18 May 2009 to reflect the changes we reported in our talk presented to the FMCS in Baltimore.
• The next major update was done on 5 January 2011.
• An update was undertaken on 4 October 2011 to accommodate the new classification applied on this site.
• Another update was undertaken in preparation for sharing the MUSSELpdb with ITIS on 11 August 2013.
• A subsequent update went live 15 November 2014 after completing our obligation to ITIS.
• We did a major update on 5 December 2017 because it had been a long time.
• After less than four months, we did another update on 30 March 2018 to accommodate a number of new species and genera.
• But most recent update was released on 8 August 2018 to incorporate some major changes in higher classification.

We currently estimate the global diversity of freshwater mussels at 927 species in 179 genera. The discussion on this web site will proceed along two parallel paths:

• Taxonomy: the organization is based upon freshwater mussel families.
• Geography: the organization is based upon geographical assemblages of freshwater mussels.