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

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs ...

, an aquatic bivalve

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Unionidae The Unionidae are a 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 at its most divers ...

, 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. 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 (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, 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) (the ''Act'') 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 D ...

listed it in the

List of Wildlife Species at Risk The List of Wildlife Species at Risk currently has more than 800 entries for Canadian wild life species considered vulnerable; including 363 classified as endangered species, —190 threatened species, —235 special concern, and 22 extirpated ...

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 Bivalve genera Monotypic mollusc genera Bivalves described in 1839 {{Unionidae-stub