''Gonidea angulata'', the western ridged mussel or Rocky Mountain ridged mussel, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

freshwater mussel Freshwater bivalves are molluscs of the order Bivalvia that inhabit freshwater ecosystems. They are one of the two main groups of freshwater molluscs, along with freshwater snails. The majority of bivalve molluscs are saltwater species that l ...

, an

aquatic Aquatic means relating to water; living in or near water or taking place in water; does not include groundwater, as "aquatic" implies an environment where plants and animals live. Aquatic(s) may also refer to: * Aquatic animal, either vertebrate ...

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the family

Unionidae The Unionidae are a Family (biology), family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is a ...

, the river mussels. It is the only species in the genus ''Gonidea''.

Description

Shell is 125 mm long, 65 mm high, 40 mm wide.

Distribution

The western ridged mussel historically occurred in river basins spanning portions of the western states of California, Idaho, Nevada, Oregon, and Washington, and the Canadian province of British Columbia.

Conservation status

The western ridged mussel has declined significantly throughout much of its range in western

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. Research indicates that the species has experienced a significant reduction in range from the historic distribution (43%), with the southern extent of the species’ range in California having contracted northward approximately 475 miles as compared to the historic range. Live western ridged mussels were not detected at 46% of the 87 sites where it historically occurred and that have been recently revisited. In Canada, it lives in

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, where the

Committee on the Status of Endangered Wildlife in Canada The Committee on the Status of Endangered Wildlife in Canada (COSEWIC, French: Comité sur la situation des espèces en péril au Canada, COSEPAC) is an independent committee of wildlife experts and scientists whose "raison d'être is to identify s ...

(COSEWIC) has listed it as a species of special concern. The Canadian

Species at Risk Act The ''Species at Risk Act'' (, SARA) is a piece of Canadian federal legislation which became law in Canada on December 12, 2002. It is designed to meet one of Canada's key commitments under the International Convention on Biological Diversity. T ...

listed it in the

List of Wildlife Species at Risk As of November 2024, the List of Wildlife Species at Risk has more than 600 entries for Canadian wildlife species considered at varying risks of extinction, including 301 classified as endangered species, 147 threatened species, 200 special conc ...

as being a species of special concern in Canada in 2003, and as endangered in 2010.COSEWIC. 2011

. COSEWIC, Committee on the Status of Endangered Wildlife in Canada

References

Unionidae Monotypic bivalve genera Bivalves described in 1839 {{Unionidae-stub