''Theliderma stapes'', the stirrup shell or stirrupshell, was a species of

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 ...

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 ...

. It was

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to eastern

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

and western

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

in the United States. It was last observed in 1987 and was proposed for delisting due to extinction by the

US Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is a U.S. federal government agency within the United States Department of the Interior which oversees the management of fish, wildlife, and natural habitats in the United States. ...

in 2021. It was officially declared extinct on October 16, 2023.

Conservation

This species experienced a population collapse primarily due to river modification in the form of canal construction. In 1976, it was predicted that the construction of the

Tennessee–Tombigbee Waterway The Tennessee–Tombigbee Waterway (popularly known as the Tenn-Tom) is a artificial waterway built in the 20th century from the Tennessee River to the junction of the Black Warrior- Tombigbee River system near Demopolis, Alabama, United State ...

would cause the extinction of this species. This prediction would quickly come to fruition after the waterway was completed in 1984. Freshly dead shells of this species were last observed in 1987 and further surveys have failed to find any evidence of a surviving population. In 2021, it was proposed to delist this species from the

Endangered Species Act The Endangered Species Act of 1973 (ESA; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting and conserving imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of e ...

. This is done when further efforts to recover a species would almost certainly be futile, and there is no evidence of currently surviving individuals. The species was delisted effective November 16, 2023.

References

stapes The ''stapes'' or stirrup is a bone in the middle ear of humans and other tetrapods which is involved in the conduction of sound vibrations to the inner ear. This bone is connected to the oval window by its annular ligament, which allows the f ...

Endemic molluscs of the United States Critically endangered fauna of the United States Bivalves described in 1831 Taxonomy articles created by Polbot {{Unionidae-stub