Medionidus simpsonianus Walker, 1905

Ochlockonee moccasinshell

Taxonomy & Nomenclature

Conservation Status

Last record: 1993 (USFWS, 2003a,b; Suckling et al. 2004); 1995 (FFWCC, n.d.)

Rediscovered in: 2007 (source [deadlink]); 2014 (Holcomb et al., 2015)

IUCN RedList status: Critically Endangered

Distribution & Habitat

Ochloknee River system, Florida & Georgia, USA

Biology & Ecology

Hypodigm

Media

References

Original scientific description:

Walker, B. (1905). A new species of Medionidus. The Nautilus 18(12): 136-137, plate 9.

Other references:

Baillie, J. and Groombridge, B. (eds). (1996). 1996 IUCN Red List of Threatened Animals. pp. 378. International Union for Conservation of Nature, Gland, Switzerland and Cambridge, UK.

Bogan, Arthur E. (Mollusc Specialist Group). (2000). Medionidus simpsonianus. The IUCN Red List of Threatened Species 2000: e.T12929A3399109. https://dx.doi.org/10.2305/IUCN.UK.2000.RLTS.T12929A3399109.en. Accessed on 05 July 2025.

Burch, J. B. (1975). Freshwater unionacean clams (Mollusca: Pelecypoda) of North America. Malacological Publications: Hamburg, Michigan. 204 pp.

Clench, W. J. and Turner, R. D. (1956). Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River. Bulletin of the Florida State Museum, Biological Sciences 1: 97-239.

FFWCC (Florida Fish and Wildlife Conservation Commission). (n.d.). Freshwater Mussel Rediscovered. Available at: https://myfwc.com/research/freshwater/species-assessments/mollusks/moccasinshell/ [Accessed 5 July 2025]

Frierson, L. S. (1927). A Classified and Annotated Checklist of the North American Niades. Waco, Texas: Baylor University Press. 111 pp.

Graf, Daniel L. and Cummings, Kevin S. (2021). A ‘big data’ approach to global freshwater mussel diversity (Bivalvia: Unionoida), with an updated checklist of genera and species. Journal of Molluscan Studies 87(1): eyaa034 (36 pp.). https://doi.org/10.1093/mollus/eyaa034

Graf, Daniel L. and Cummings, Kevin S. (2025). The Freshwater Mussels (Unionoida) of the World (and other less consequential bivalves). MUSSEL Project Web Site, https://www.mussel-project.net/. Accessed 5 July 2025.

Haas, F. (1969). Superfamilia Unionacea. Das Tierreich 88: x, 1-663. Berlin: Walter de Gruyter & Co.

Hilton-Taylor, Craig. (2000). 2000 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, UK.

Holcomb, Jordan, Rowe, Matthew, Williams, Jim and Pursifull, Sandra. (2015). Discovery of the Ochlockonee moccasinshell, Medionidus simpsonianus, in the lower Ochlockonee River, Florida. Southeastern Naturalist 14(4): 714−720.

Hopper, G. W., Bucholz, J. R., DuBose, T. P., Fogelman, K. J., Keogh, S. M. et al. (2023). A trait dataset for freshwater mussels of the United States of America. Scientific Data 10: 745 (pp. 1-15). https://doi.org/10.1038/s41597-023-02635-9

MolluscaBase eds. (2025). MolluscaBase. Medionidus simpsonianus B. Walker, 1905. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=857241 on 2025-07-05

Simpson, Charles Torrey. (1914). A descriptive catalogue of the naiades, or pearly fresh-water mussels. Parts I-III. Detroit, Michigan: Bryant Walker. 1540 pp.

Suckling, Kieran, Slack, Rhiwena and Nowicki, Brian. (2004). Extinct and the Endangered Species Act. Centre For Biological Diversity. 63 pp.

USFWS. (2003a). Ochlockonee Moccasinshell (Medionidus simpsonianus) 5-Year Review: Summary and Evaluation. Panama City, Florida, U.S. Fish and Wildlife Service.

USFWS. (2003b). Recovery Plan for endangered fat threeridge (Amblema neislerii), shinyrayed pocketbook (Lampsilis subangulata), gulf moccasinshell (Medionidus penicillatus), Ochlockonee moccasinshell (Medionidus simpsonianus), and oval pigtoe (Pleurobema pyriforme); and threatened chipola slabshell (Elliptio chipolaensis), and purple bankclimber (Elliptoideus sloatianus). U.S. Fish and Wildlife Service, Southeast Region, Atlanta, Georgia. 142 pp. Available at: http://ecos.fws.gov/docs/recovery_plans/2003/030930.pdf

Williams, James D., Bogan, Arthur E., Butler, Robert S., Cummings, Kevin S., Garner, Jeffrey T., Harris, John L., Johnson, Nathan A. and Watters, G. Thomas. (2017). A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20(2): 33-58. https://doi.org/10.31931/fmbc.v20i2.2017.33-58

Williams, James D., Butler, R. S., Warren, G. L. and Johnson, N. A. (2014). Freshwater Mussels of Florida. Tuscaloosa, AL: University of Alabama Press. 498 pp.

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