# Unionidae

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> Source revision: 1355283255
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Family of molluscs

Unionidae Temporal range: Middle Jurassic - present, 177–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N Six endangered species of Unionidae Scientific classification Kingdom: Animalia Phylum: Mollusca Class: Bivalvia Order: Unionida Superfamily: Unionoidea Family: Unionidae Fleming, 1828 Genera See text

The **Unionidae** are a [family](/source/Family_(taxonomy)) of [freshwater mussels](/source/Freshwater_mussel), the largest in the order [Unionida](/source/Unionida), the [bivalve](/source/Bivalve) [molluscs](/source/Mollusc) sometimes known as river mussels, or simply as unionids.[1][2]

The range of distribution for this family is world-wide. It is at its most diverse in North America, with about 297 recognised taxa,[3][4][5] but China and Southeast Asia also support very diverse faunas.

Freshwater mussels occupy a wide range of habitats, but most often occupy [lotic](/source/Lotic) waters, i.e. flowing water such as rivers, streams and creeks.

## Origin and early diversification

The recent phylogenetic study reveals that the Unionidae most likely originated in Southeast and East Asia in the Jurassic, with the earliest expansions into North America and Africa (since the mid-Cretaceous) followed by the colonization of Europe and India (since the Paleocene).[6]

## Life history

Unionidae burrow into the substrate, with their posterior margins exposed. They pump water through the incurrent [aperture](/source/Aperture_(mollusc)), obtaining [oxygen](/source/Oxygen) and food. They remove phytoplankton and zooplankton, as well as suspended bacteria, fungal spores, and dissolved organic matter.[7][8][9][10][11][12][13][14][15][16] Despite extensive laboratory studies, which of these filtrates unionoids actually process remains uncertain. In high densities, they have the ability to influence water clarity[17][18] but filtration rates are dependent on water temperature, current velocity, and particle size and concentration. In addition, gill morphology can determine particle size filtered, as well as the rate.[11]

## Reproduction

[Aggressive mimicry](/source/Aggressive_mimicry) in *[Lampsilis fasciola](/source/Lampsilis_fasciola)*

Unionidae are distinguished by a unique and complex lifecycle. Most unionids are of separate sex, although some species, such as *[Elliptio complanata](/source/Elliptio_complanata)*, are known to be [hermaphroditic](/source/Hermaphrodite).[19]

The sperm is ejected from the [mantle](/source/Mantle_(mollusc)) cavity through the male's excurrent aperture and taken into the female's mantle cavity through the incurrent aperture. Fertilised eggs move from the gonads to the gills ([marsupia](https://en.wikipedia.org/w/index.php?title=Marsupia&action=edit&redlink=1)) where they further ripen and metamorph into [glochidia](/source/Glochidium), the first larval stage. Mature glochidia are released by the female and then attach to the [gills](/source/Gill), fins, or skin of a host [fish](/source/Fish). A cyst is quickly formed around the glochidia, and they stay on the fish for several weeks or months before they fall off as [juvenile](/source/Juvenile_(organism)) [mussels](/source/Mussels), which then bury themselves in the sediment.

Some of the species in the Unionidae, notably in the [Lampsilini](/source/Lampsilini) tribe, have evolved a remarkable reproductive strategy. The edge of the female's body that protrudes from the valves of the shell develops into an imitation of a small fish complete with markings and false eyes. This decoy moves in the current and attracts the attention of real fish. Some fish see the decoy as prey, while others see a [conspecific](/source/Conspecific), i.e. a member of their own species. Whatever they see, they approach for a closer look and the mussel releases huge numbers of larvae from her gills, dousing the inquisitive fish with her tiny, parasitic young. These glochidial larvae are drawn into the fish's gills, where they attach and trigger a tissue response that forms a small [cyst](/source/Cyst) in which the young mussel resides. It feeds by breaking down and digesting the tissue of the fish within the cyst.[20]

Sex is determined by a region located on the mitochondrial DNA, the male [open reading frame](/source/Open_reading_frame) (M-ORF) and female open-reading frame (F-ORF). Hermaphroditic mussels lack these regions and contain a female-like open-reading frame dubbed hermaphroditic open-reading frame (H-ORF). In many mussels, the hermaphroditic state is ancestral and the male sex evolved later. This region of the mitochondria also may be responsible for the evolution of doubly uniparental inheritance seen in freshwater mussels.[21]

## Taxonomy

### Genera by taxonomic order

The following classification is based on MolluscaBase and the MUSSEL Project database:[22][23]

- Subfamily [Ambleminae](/source/Ambleminae) - Tribe [Lampsilini](/source/Lampsilini) - Genus *[Epioblasma](/source/Epioblasma)* - Genus *[Lampsilis](/source/Lampsilis)* - Genus *[Potamilus](/source/Potamilus)* - Genus *[Actinonaias](/source/Actinonaias)* - Genus *[Cambarunio](https://en.wikipedia.org/w/index.php?title=Cambarunio&action=edit&redlink=1)* - Genus *[Obovaria](/source/Obovaria)* - Genus *[Toxolasma](/source/Toxolasma)* - Genus *[Medionidus](/source/Medionidus)* - Genus *[Ptychobranchus](/source/Ptychobranchus)* - Genus *[Disconaias](/source/Disconaias)* - Genus *[Leaunio](https://en.wikipedia.org/w/index.php?title=Leaunio&action=edit&redlink=1)* - Genus *[Venustaconcha](/source/Venustaconcha)* - Genus *[Cyrtonaias](/source/Cyrtonaias)* - Genus *[Hamiota](/source/Hamiota_(bivalve))* - Genus *[Sagittunio](/source/Sagittunio)* - Genus *[Truncilla](/source/Truncilla)* - Genus *[Villosa](/source/Villosa)* - Genus *[Arotonaias](https://en.wikipedia.org/w/index.php?title=Arotonaias&action=edit&redlink=1)* - Genus *[Cyprogenia](/source/Cyprogenia)* - Genus *[Delphinonaias](/source/Delphinonaias)* - Genus *[Ortmanniana](https://en.wikipedia.org/w/index.php?title=Ortmanniana&action=edit&redlink=1)* - Genus *[Pachynaias](https://en.wikipedia.org/w/index.php?title=Pachynaias&action=edit&redlink=1)* - Genus *[Atlanticoncha](/source/Atlanticoncha)* - Genus *[Dromus](/source/Dromus_(mollusc))* - Genus *[Ellipsaria](/source/Ellipsaria)* - Genus *[Friersonia](https://en.wikipedia.org/w/index.php?title=Friersonia&action=edit&redlink=1)* - Genus *[Glebula](/source/Glebula)* - Genus *[Lemiox](/source/Lemiox)* - Genus *[Ligumia](/source/Ligumia)* - Genus *[Obliquaria](/source/Obliquaria)* - Genus *[Paetulunio](/source/Paetulunio)* - Tribe [Pleurobemini](/source/Pleurobemini) - Genus *[Elliptio](/source/Elliptio)* - Genus *[Pleurobema](/source/Pleurobema)* - Genus *[Fusconaia](/source/Fusconaia)* - Genus *[Plethobasus](/source/Plethobasus)* - Genus *[Pleuronaia](/source/Pleuronaia)* - Genus *[Parvaspina](/source/Parvaspina)* - Genus *[Elliptoideus](/source/Elliptoideus)* - Genus *[Eurynia](https://en.wikipedia.org/w/index.php?title=Eurynia&action=edit&redlink=1)* - Genus *[Hemistena](/source/Hemistena)* - Tribe [Popenaiadini](/source/Popenaiadini) - Genus *[Nephronaias](https://en.wikipedia.org/w/index.php?title=Nephronaias&action=edit&redlink=1)* - Genus *[Psoronaias](/source/Psoronaias)* - Genus *[Barynaias](https://en.wikipedia.org/w/index.php?title=Barynaias&action=edit&redlink=1)* - Genus *[Popenaias](/source/Popenaias)* - Genus *[Sphenonaias](https://en.wikipedia.org/w/index.php?title=Sphenonaias&action=edit&redlink=1)* - Genus *[Micronaias](https://en.wikipedia.org/w/index.php?title=Micronaias&action=edit&redlink=1)* - Genus *[Nephritica](https://en.wikipedia.org/w/index.php?title=Nephritica&action=edit&redlink=1)* - Genus *[Reticulatus](https://en.wikipedia.org/w/index.php?title=Reticulatus&action=edit&redlink=1)* - Genus *[Martensnaias](https://en.wikipedia.org/w/index.php?title=Martensnaias&action=edit&redlink=1)* - Tribe [Quadrulini](/source/Quadrulini) - Genus *[Cyclonaias](/source/Cyclonaias)* - Genus *[Theliderma](/source/Theliderma)* - Genus *[Uniomerus](/source/Uniomerus)* - Genus *[Quadrula](/source/Quadrula)* - Genus *[Megalonaias](/source/Megalonaias)* - Genus *[Tritogonia](https://en.wikipedia.org/w/index.php?title=Tritogonia&action=edit&redlink=1)* - Tribe [Amblemini](/source/Amblemini) - Genus *[Amblema](/source/Amblema)* - Genus *[Reginaia](/source/Reginaia)* - Genus *[Plectomerus](/source/Plectomerus)*

- Subfamily [Unioninae](/source/Unioninae) - Tribe [Anodontini](/source/Anodontini) - Subtribe [Alasmidontina](https://en.wikipedia.org/w/index.php?title=Alasmidontina&action=edit&redlink=1) - Genus *[Alasmidonta](/source/Alasmidonta)* - Genus *[Lasmigona](/source/Lasmigona)* - Genus *[Ligodonta](/source/Ligodonta)* - Genus *[Pyganodon](/source/Pyganodon)* - Genus *[Utterbackiana](https://en.wikipedia.org/w/index.php?title=Utterbackiana&action=edit&redlink=1)* - Genus *[Strophitus](/source/Strophitus)* - Genus *[Utterbackia](/source/Utterbackia)* - Genus *[Anodontoides](/source/Anodontoides)* - Genus *[Arcidens](/source/Arcidens)* - Genus *[Pseudodontoideus](https://en.wikipedia.org/w/index.php?title=Pseudodontoideus&action=edit&redlink=1)* - Genus *[Pegias](/source/Pegias)* - Genus *[Simpsonaias](/source/Simpsonaias)* - Subtribe [Cristariina](https://en.wikipedia.org/w/index.php?title=Cristariina&action=edit&redlink=1) - Genus *[Sinanodonta](https://en.wikipedia.org/w/index.php?title=Sinanodonta&action=edit&redlink=1)* - Genus *[Buldowskia](https://en.wikipedia.org/w/index.php?title=Buldowskia&action=edit&redlink=1)* - Genus *[Cristaria](/source/Cristaria_(bivalve))* - Genus *[Anemina](https://en.wikipedia.org/w/index.php?title=Anemina&action=edit&redlink=1)* - Genus *[Beringiana](https://en.wikipedia.org/w/index.php?title=Beringiana&action=edit&redlink=1)* - Genus *[Pletholophus](https://en.wikipedia.org/w/index.php?title=Pletholophus&action=edit&redlink=1)* - Genus *[Simpsonella](https://en.wikipedia.org/w/index.php?title=Simpsonella&action=edit&redlink=1)* - Genus *[Amuranodonta](https://en.wikipedia.org/w/index.php?title=Amuranodonta&action=edit&redlink=1)* - Subtribe [Anodontina](https://en.wikipedia.org/w/index.php?title=Anodontina&action=edit&redlink=1) - Genus *[Anodonta](/source/Anodonta)* - Genus *[Pseudanodonta](/source/Pseudanodonta)* - Tribe [Unionini](/source/Unionini) - Genus *[Unio](/source/Unio_(bivalve))* - Genus *[Nodularia](https://en.wikipedia.org/w/index.php?title=Nodularia_(bivalve)&action=edit&redlink=1)* - Genus *[Aculamprotula](https://en.wikipedia.org/w/index.php?title=Aculamprotula&action=edit&redlink=1)* - Genus *[Acuticosta](https://en.wikipedia.org/w/index.php?title=Acuticosta&action=edit&redlink=1)* - Genus *[Cuneopsis](https://en.wikipedia.org/w/index.php?title=Cuneopsis&action=edit&redlink=1)* - Genus *[Inversiunio](https://en.wikipedia.org/w/index.php?title=Inversiunio&action=edit&redlink=1)* - Genus *[Pseudobaphia](https://en.wikipedia.org/w/index.php?title=Pseudobaphia&action=edit&redlink=1)* - Genus *[Rhombuniopsis](https://en.wikipedia.org/w/index.php?title=Rhombuniopsis&action=edit&redlink=1)* - Genus *[Lepidodesma](https://en.wikipedia.org/w/index.php?title=Lepidodesma&action=edit&redlink=1)* - Genus *[Pseudocuneopsis](https://en.wikipedia.org/w/index.php?title=Pseudocuneopsis&action=edit&redlink=1)* - Genus *[Schistodesmus](https://en.wikipedia.org/w/index.php?title=Schistodesmus&action=edit&redlink=1)* - Genus *[Arcuneopsis](https://en.wikipedia.org/w/index.php?title=Arcuneopsis&action=edit&redlink=1)* - Genus *[Diaurora](https://en.wikipedia.org/w/index.php?title=Diaurora&action=edit&redlink=1)* - Genus *[Middendorffinaia](/source/Middendorffinaia)* - Genus *[Protunio](https://en.wikipedia.org/w/index.php?title=Protunio&action=edit&redlink=1)* - Tribe [Lanceolariini](https://en.wikipedia.org/w/index.php?title=Lanceolariini&action=edit&redlink=1) - Genus *[Lanceolaria](https://en.wikipedia.org/w/index.php?title=Lanceolaria&action=edit&redlink=1)*

- Subfamily [Gonideinae](https://en.wikipedia.org/w/index.php?title=Gonideinae&action=edit&redlink=1) - Tribe [Pseudodontini](https://en.wikipedia.org/w/index.php?title=Pseudodontini&action=edit&redlink=1) - Subtribe [Pilsbryoconchina](https://en.wikipedia.org/w/index.php?title=Pilsbryoconchina&action=edit&redlink=1) - Genus *[Sundadontina](https://en.wikipedia.org/w/index.php?title=Sundadontina&action=edit&redlink=1)* - Genus *[Monodontina](https://en.wikipedia.org/w/index.php?title=Monodontina&action=edit&redlink=1)* - Genus *[Pilsbryoconcha](/source/Pilsbryoconcha)* - Genus *[Bineurus](https://en.wikipedia.org/w/index.php?title=Bineurus&action=edit&redlink=1)* - Genus *[Thaiconcha](https://en.wikipedia.org/w/index.php?title=Thaiconcha&action=edit&redlink=1)* - Genus *[Namkongnaia](https://en.wikipedia.org/w/index.php?title=Namkongnaia&action=edit&redlink=1)* - Genus *[Nyeinchanconcha](https://en.wikipedia.org/w/index.php?title=Nyeinchanconcha&action=edit&redlink=1)* - Subtribe [Pseudodontina](https://en.wikipedia.org/w/index.php?title=Pseudodontina&action=edit&redlink=1) - Genus *[Pseudodon](/source/Pseudodon)* - Tribe [Contradentini](https://en.wikipedia.org/w/index.php?title=Contradentini&action=edit&redlink=1) - Genus *[Lens](https://en.wikipedia.org/w/index.php?title=Lens_(bivalve)&action=edit&redlink=1)* - Genus *[Yaukthwa](/source/Yaukthwa)* - Genus *[Physunio](https://en.wikipedia.org/w/index.php?title=Physunio&action=edit&redlink=1)* - Genus *[Trapezoideus](https://en.wikipedia.org/w/index.php?title=Trapezoideus&action=edit&redlink=1)* - Genus *[Pressidens](https://en.wikipedia.org/w/index.php?title=Pressidens&action=edit&redlink=1)* - Genus *[Solenaia](/source/Solenaia)* - Tribe [Lamprotulini](https://en.wikipedia.org/w/index.php?title=Lamprotulini&action=edit&redlink=1) - Genus *[Lamprotula](https://en.wikipedia.org/w/index.php?title=Lamprotula&action=edit&redlink=1)* - Genus *[Potomida](/source/Potomida)* - Genus *[Schepmania](https://en.wikipedia.org/w/index.php?title=Schepmania&action=edit&redlink=1)* - Genus *[Discomya](https://en.wikipedia.org/w/index.php?title=Discomya&action=edit&redlink=1)* - Genus *[Pronodularia](https://en.wikipedia.org/w/index.php?title=Pronodularia&action=edit&redlink=1)* - Tribe [Rectidentini](https://en.wikipedia.org/w/index.php?title=Rectidentini&action=edit&redlink=1) - Genus *[Hyriopsis](/source/Hyriopsis)* - Genus *[Ensidens](https://en.wikipedia.org/w/index.php?title=Ensidens&action=edit&redlink=1)* - Genus *[Ctenodesma](https://en.wikipedia.org/w/index.php?title=Ctenodesma&action=edit&redlink=1)* - Genus *[Elongaria](https://en.wikipedia.org/w/index.php?title=Elongaria&action=edit&redlink=1)* - Genus *[Khairuloconcha](https://en.wikipedia.org/w/index.php?title=Khairuloconcha&action=edit&redlink=1)* - Genus *[Prohyriopsis](https://en.wikipedia.org/w/index.php?title=Prohyriopsis&action=edit&redlink=1)* - Genus *[Rectidens](https://en.wikipedia.org/w/index.php?title=Rectidens&action=edit&redlink=1)* - Tribe [Gonideni](https://en.wikipedia.org/w/index.php?title=Gonideni&action=edit&redlink=1) - Genus *[Ptychorhynchus](https://en.wikipedia.org/w/index.php?title=Ptychorhynchus&action=edit&redlink=1)* - Genus *[Sinosolenaia](https://en.wikipedia.org/w/index.php?title=Sinosolenaia&action=edit&redlink=1)* - Genus *[Inversidens](https://en.wikipedia.org/w/index.php?title=Inversidens&action=edit&redlink=1)* - Genus *[Leguminaia](https://en.wikipedia.org/w/index.php?title=Leguminaia&action=edit&redlink=1)* - Genus *[Parvasolenaia](https://en.wikipedia.org/w/index.php?title=Parvasolenaia&action=edit&redlink=1)* - Genus *[Gonidea](/source/Gonidea)* - Genus *[Koreosolenaia](https://en.wikipedia.org/w/index.php?title=Koreosolenaia&action=edit&redlink=1)* - Genus *[Microcondylaea](/source/Microcondylaea)* - Genus *[Obovalis](https://en.wikipedia.org/w/index.php?title=Obovalis&action=edit&redlink=1)* - Genus *[Pseudodontopsis](https://en.wikipedia.org/w/index.php?title=Pseudodontopsis&action=edit&redlink=1)* - Tribe [Chamberlainini](https://en.wikipedia.org/w/index.php?title=Chamberlainini&action=edit&redlink=1) - Genus *[Sinohyriopsis](https://en.wikipedia.org/w/index.php?title=Sinohyriopsis&action=edit&redlink=1)* - Genus *[Chamberlainia](https://en.wikipedia.org/w/index.php?title=Chamberlainia_(bivalve)&action=edit&redlink=1)* - Genus *[Caudiculatus](https://en.wikipedia.org/w/index.php?title=Caudiculatus&action=edit&redlink=1)*

- Subfamily [Parreysiinae](https://en.wikipedia.org/w/index.php?title=Parreysiinae&action=edit&redlink=1) - Tribe [Coelaturini](https://en.wikipedia.org/w/index.php?title=Coelaturini&action=edit&redlink=1) - Genus *[Coelatura](/source/Coelatura)* - Genus *[Nitia](https://en.wikipedia.org/w/index.php?title=Nitia_(bivalve)&action=edit&redlink=1)* - Genus *[Nyassunio](https://en.wikipedia.org/w/index.php?title=Nyassunio&action=edit&redlink=1)* - Genus *[Prisodontopsis](https://en.wikipedia.org/w/index.php?title=Prisodontopsis&action=edit&redlink=1)* - Genus *[Brazzaea](https://en.wikipedia.org/w/index.php?title=Brazzaea&action=edit&redlink=1)* - Genus *[Grandidieria](https://en.wikipedia.org/w/index.php?title=Grandidieria&action=edit&redlink=1)* - Genus *[Moncetia](https://en.wikipedia.org/w/index.php?title=Moncetia&action=edit&redlink=1)* - Genus *[Pseudospatha](/source/Pseudospatha)* - Tribe [Indochinellini](https://en.wikipedia.org/w/index.php?title=Indochinellini&action=edit&redlink=1) - Genus *[Indonaia](https://en.wikipedia.org/w/index.php?title=Indonaia&action=edit&redlink=1)* - Genus *[Scabies](/source/Scabies_(bivalve))* - Genus *[Radiatula](https://en.wikipedia.org/w/index.php?title=Radiatula&action=edit&redlink=1)* - Genus *[Harmandia](https://en.wikipedia.org/w/index.php?title=Harmandia_(bivalve)&action=edit&redlink=1)* - Genus *[Indochinella](https://en.wikipedia.org/w/index.php?title=Indochinella&action=edit&redlink=1)* - Genus *[Scabiellus](https://en.wikipedia.org/w/index.php?title=Scabiellus&action=edit&redlink=1)* - Genus *[Unionetta](https://en.wikipedia.org/w/index.php?title=Unionetta&action=edit&redlink=1)* - Tribe [Lamellidentini](https://en.wikipedia.org/w/index.php?title=Lamellidentini&action=edit&redlink=1) - Genus *[Lamellidens](https://en.wikipedia.org/w/index.php?title=Lamellidens&action=edit&redlink=1)* - Genus *[Trapezidens](https://en.wikipedia.org/w/index.php?title=Trapezidens&action=edit&redlink=1)* - Genus *[Arcidopsis](https://en.wikipedia.org/w/index.php?title=Arcidopsis&action=edit&redlink=1)* - Tribe [Leoparreysiini](https://en.wikipedia.org/w/index.php?title=Leoparreysiini&action=edit&redlink=1) - Genus *[Leoparreysia](https://en.wikipedia.org/w/index.php?title=Leoparreysia&action=edit&redlink=1)* - Tribe [Parreysiini](https://en.wikipedia.org/w/index.php?title=Parreysiini&action=edit&redlink=1) - Genus *[Parreysia](https://en.wikipedia.org/w/index.php?title=Parreysia&action=edit&redlink=1)* - Genus *[Balwantia](https://en.wikipedia.org/w/index.php?title=Balwantia&action=edit&redlink=1)*

- Genus *[Haasodonta](https://en.wikipedia.org/w/index.php?title=Haasodonta&action=edit&redlink=1)* (subfamily *incertae sedis*)

- Genus *[Germainaia](https://en.wikipedia.org/w/index.php?title=Germainaia&action=edit&redlink=1)* (subfamily *incertae sedis*)

- Genus *[Tacuaremboia](/source/Tacuaremboia)* (subfamily *incertae sedis*)

- Subfamily [Modellnaiinae](https://en.wikipedia.org/w/index.php?title=Modellnaiinae&action=edit&redlink=1) - Genus *[Modellnaia](https://en.wikipedia.org/w/index.php?title=Modellnaia&action=edit&redlink=1)*

### Genera by alphabetic order and region

Widespread Anodonta Potomida Unio Africa Brazzaea Coelatura Germainaia Grandidieria Mweruella Nitia Nyassunio Prisodontopsis Pseudospatha Central America and Mexico Arotonaias Barynaias Cyrtonaias Delphinonaias Disconaias Friersonia Martensnaias Micronaias Nephritica Nephronaias Pachynaias Popenaias Psoronaias Psorula Reticulatus Sphenonaias Eastern Asia Aculamprotula Acuticosta Anemina Arconaia BineurusC. T. Simpson, 1900 Caudiculatus Chamberlainia Contradens Cristaria Ctenodesma Cuneopsis Discomya Elongaria Ensidens Harmandia Hyriopsis Inversidens Inversiunio Lamprotula Lanceolaria Lepidodesma Modellnaia Monodontina Conrad, 1853 Nodularia Oxynaia Physunio Pilsbryoconcha Pressidens Prohyriopsis Pronodularia Protunio Pseudobaphia Pseudodon Ptychorhynchus Rectidens Rhombuniopsis Scabies Schepmania Schistodesmus Simpsonella Sinanodonta Solenaia Sundadontina Bolotov et al., 2020 Thaiconcha Bolotov et al., 2020 Unionetta Europe Microcondylaea Pseudanodonta India Arcidopsis Lamellidens Parreysia Radiatula Trapezoideus Yaukthwa Middle East Leguminaia Pseudodontopsis New Guinea Haasodonta North America Actinonaias Alasmidonta Amblema Anodontoides Arcidens Cyprogenia Dromus Ellipsaria Elliptio Elliptoideus Epioblasma Fusconaia Glebula Gonidea Hamiota Hemistena Lampsilis Lasmigona Lemiox Leptodea Ligumia Medionidus Megalonaias Obliquaria Obovaria Pegias Plectomerus Plethobasus Pleurobema Pleuronaia Potamilus Psoronaias Crosse & P. Fischer, 1894 Ptychobranchus Pyganodon Quadrula Reginaia Rotundaria Simpsonaias Strophitus Theliderma Toxolasma Truncilla Uniomerus Utterbackia Venustaconcha Villosa South America Tacuaremboia

## Fossilization and taphonomic implications

In large enough quantities, unionid shells can have enough of an impact on environmental conditions to affect the ability of organic remains in the local environment to fossilize.[24] For example, in the [Dinosaur Park Formation](/source/Dinosaur_Park_Formation), fossil hadrosaur eggshell is rare[24] because the breakdown of [tannins](/source/Tannins) from local [coniferous](/source/Coniferous) vegetation would have caused the ancient waters to become acidic.[24] Eggshell fragments are present in only two [microfossil](/source/Microfossil) sites, both of which are dominated by the preserved shells of invertebrate life, including unionids.[24] The slow dissolution of these shells releasing [calcium carbonate](/source/Calcium_carbonate) into the water raised the water's [pH](/source/PH) high enough to prevent the eggshell fragments from dissolving before they could be fossilized.[24]

## References

1. **[^](#cite_ref-WoRMS_1-0)** [Unionidae](http://www.marinespecies.org/aphia.php?p=taxdetails&id=160333). Retrieved through: [World Register of Marine Species](/source/World_Register_of_Marine_Species) on 4 January 2012.

1. **[^](#cite_ref-CompBiv_2-0)** Huber, Markus (2010). *Compendium of Bivalves. A Full-color Guide to 3'300 of the World's Marine Bivalves. A Status on Bivalvia after 250 Years of Research*. Hackenheim: ConchBooks. pp. 901 pp. + CD. [ISBN](/source/ISBN_(identifier)) [978-3-939767-28-2](https://en.wikipedia.org/wiki/Special:BookSources/978-3-939767-28-2).

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1. **[^](#cite_ref-6)** Bolotov, I.N., Kondakov, A.V., Vikhrev, I.V., Aksenova, O.V., Bespalaya, Y.V. Gofarov, M.Y., Kolosova, Y.S., Konopleva, E.S., Spitsyn, V.M., Tanmuangpak, K. & Tumpeesuwan, S. (2017). Ancient River Inference Explains Exceptional Oriental Freshwater Mussel Radiations.Scientific Reports 7: 2135, [doi:10.1038/s41598-017-02312-z](https://doi.org/10.1038/s41598-017-02312-z)

1. **[^](#cite_ref-7)** Allan, W. R. (1914). "The food and feeding habits of freshwater mussels." Biological Bulletin 27: 127-147.

1. **[^](#cite_ref-8)** Coker, R. E., Shira, A.F., Clark, H.W., Howard, A.D. (1921). "Natural history and propagation of fresh-water mussels." Bulletin of the Bureau of Fisheries 37: 77-181.

1. **[^](#cite_ref-9)** Churchill, E. P., Lewis, S.I. (1924). "Food and feeding in fresh-water mussels." Bulletin of the Bureau of Fisheries 39: 439-471.

1. **[^](#cite_ref-10)** McMahon, R. F., Bogan, A.E. (2001). Mollusca: Bivalvia. Ecology and classification of North American freshwater invertebrates. J. H. Thorp, Covich, A.P. San Diego, Academic Press: 331-429.

1. ^ [***a***](#cite_ref-Silverman,_H._1997_11-0) [***b***](#cite_ref-Silverman,_H._1997_11-1) Silverman, H., Nichols S.J, Cherry J.S., Archberger E., Lynn J.S., Dietz T.H. (1997). "Clearance of laboratory-cultured bacteria by freshwater bivalves: differences between lentic and lotic unionids." Canadian Journal of Zoology 75: 1857-1866.

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1. **[^](#cite_ref-22)** ["MUSSELpdb | family Unionidae"](https://mussel-project.uwsp.edu/fmuotwaolcb/Unionidae.html). *mussel-project.uwsp.edu*. Retrieved 2022-10-28.

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1. ^ [***a***](#cite_ref-tanke-brett-surman-2001_24-0) [***b***](#cite_ref-tanke-brett-surman-2001_24-1) [***c***](#cite_ref-tanke-brett-surman-2001_24-2) [***d***](#cite_ref-tanke-brett-surman-2001_24-3) [***e***](#cite_ref-tanke-brett-surman-2001_24-4) Tanke, D.H. and Brett-Surman, M.K. 2001. Evidence of Hatchling and Nestling-Size Hadrosaurs (Reptilia:Ornithischia) from Dinosaur Provincial Park (Dinosaur Park Formation: Campanian), Alberta, Canada. pp. 206-218. In: Mesozoic Vertebrate Life—New Research Inspired by the Paleontology of Philip J. Currie. Edited by D.H. Tanke and K. Carpenter. Indiana University Press: Bloomington. xviii + 577 pp.

## External links

Wikimedia Commons has media related to [Unionidae](https://commons.wikimedia.org/wiki/Category:Unionidae).

- [Missouri State Unio Gallery](https://web.archive.org/web/20070605035105/http://unionid.missouristate.edu/)

- [Freshwater Mollusk Conservation Society](https://web.archive.org/web/20090623000003/http://ellipse.inhs.uiuc.edu/FMCS/)

- [Ohio State University: Division of Molluscs - Freshwater Mussel Collection - Unionidae](http://www.biosci.ohio-state.edu/~molluscs/gallery/unionidae.htm) [Archived](https://web.archive.org/web/20070704150248/http://www.biosci.ohio-state.edu/~molluscs/gallery/unionidae.htm) 2007-07-04 at the [Wayback Machine](/source/Wayback_Machine)

- [Unionidae at The MUSSEL Project Web Site](https://web.archive.org/web/20090304195016/http://bama.ua.edu/~musselp/proj/grano_salis/unionidae.html)

Taxon identifiers Unionidae Wikidata: Q1434366 Wikispecies: Unionidae ADW: Unionidae BOLD: 580 CoL: 7NLH4 EoL: 2274 EPPO: 1UNIOF Fauna Europaea: 11486 Fauna Europaea (new): a8ba6f49-596c-415e-846d-cb5d62861b8a GBIF: 3461 iNaturalist: 51903 IRMNG: 114588 ITIS: 79913 NBN: NHMSYS0001702252 NCBI: 47526 Open Tree of Life: 255789 Paleobiology Database: 62728 WoRMS: 160333

Authority control databases National Czech Republic Israel Other Yale LUX

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Adapted from the Wikipedia article [Unionidae](https://en.wikipedia.org/wiki/Unionidae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Unionidae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.