| Page last updated
Wed 1 October 2025 |
The Freshwater Mussels (Unionoida) of the World (and other less consequential bivalves)
FM(U)otW(aolcb) is the web version of the MUSSEL Project Database. Follow the links to browse the data or use the custom Google search field. Either way, you win!
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For each taxon, information is provided regarding habitat,
horizon (Recent unless otherwise listed), and diversity. We are
actively working on the Recent freshwater mussels, and those are the
taxa for which the data are most complete. For other Recent freshwater
bivalves, the information largely follows
Graf (2013). For other taxa (e.g., marine, fossil), any content
is largely incidental. Bivalvia Class BIVALVIA  order UNIONOIDA: 997 Recent species.
2 genera, 1 family, 5 superfamilies
These are the freshwater mussels. There are six modern families, restricted entirely to fresh waters. In addition, there are several fossil families.
| order ADAPEDONTA: 6 Recent species.
1 superfamily | order ARCOIDA: 5 Recent species.
1 superfamily
Arcoids are primarily marine. However, one family is represented in fresh waters. |  order CARDIOIDA: 10 Recent species.
3 superfamilies
Cardioids are mostly marine, with a minor radition into freshened waters.
|  order MYOIDA: 20 Recent species.
3 superfamilies
Myoids are also primarily marine bivalves, but there are freshwater species as well, including species of the Dreissenidae.
|  order MYTILOIDA: 5 Recent species.
1 superfamily
There are a few secondarily freshwater species in this order, but otherwise mytiloids are primarily marine.
|  order SPHAERIOIDA: 272 Recent species.
1 superfamily
The Sphaeriidae is the second-most species-rich radition of bivalves into inland habitats.
|  order VENEROIDA: 96 Recent species.
5 superfamilies
The Cyrenidae represents the most significant radition of veneroids into fresh waters, but there are also a number of freshwater species in primarily marine families.
| order ARCHANODONTIDAE: fossil only.
2 genera | order LUCINOIDA: fossil only.
1 superfamily | order MODIOMORPHOIDA: fossil only.
1 superfamily | order PECTINOIDA: fossil only.
1 superfamily
An order of bivalves that has freshwater species or at least species attributed to freshwater clades. | order PTERIOIDA: fossil only.
1 superfamily
There are not really any freshwater pterioids, but at least one fossil family has been assigned to a freshwater clade. | order TRIGONIOIDA: fossil only.
2 superfamilies
Trigonioids are the marine sister-group to freshwater mussels. |
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