Epioblasma othcaloogensis (I. Lea, 1857)

Southern acornshell, Southern acorn riffle shell

Taxonomy & Nomenclature

Synonyms: Unio othcaloogensis I. Lea, 1857; Unio otcaloogensis "I. Lea, 1857" [orth. error]; Dysnomia (Penita) othcaloogensis (I. Lea, 1857); Margaron (Unio) othcaloogensis (I. Lea, 1857); Truncilla (Scalenaria) othcaloogensis (I. Lea, 1857); Truncilla (Scalenilla) othcaloogensis (I. Lea, 1857); Unio modicellus I. Lea, 1859; Dysnomia (Penita) modicella (I. Lea, 1859); Dysnomia modicella (I. Lea, 1859); Dysnomia nodicella (I. Lea, 1859); Epioblasma modicella (I. Lea, 1859); Margaron (Unio) modicellus (I. Lea, 1859); Truncilla (Truncilla) modicella (I. Lea, 1859); Truncilla modicella (I. Lea, 1859)

See Graf & Cummings (2025) for a more complete taxonomic history.

Conservation Status

Missing (Cummings & Cordeiro, 2012; Cowie et al., 2017) or Extinct (NatureServe, 2025)

Last record: 1974 (Cummings & Cordeiro, 2012; NatureServe, 2025)

IUCN RedList status: Critically Endangered (Possibly Extinct)

Distribution & Habitat

Alabama, Georgia & Tennessee, USA

Biology & Ecology

Hypodigm

Media

References

Original scientific description:

Lea, Isaac. (1857). Description of thirteen new species of uniones, from Georgia. Proceedings of the Academy of Natural Sciences of Philadelphia. 9: 31-32. [after 25 February 1857]

Other references:

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

Cowie, Robert H., Régnier, Claire, Fontaine, Benoît, and Bouchet, Philippe. (2017). Measuring the Sixth Extinction: what do mollusks tell us? The Nautilus 131(1): 3-41.

Cummings, K. and Cordeiro, J. (2012). Epioblasma othcaloogensis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. (http://www.iucnredlist.org). Downloaded on 18 July 2013.

de Gregorio, A. (1914). Su taluni molluschi di acqua dolce di America (American fresh water shells of America). Il Naturalista Siciliano 2: 31-72, pls. 3-12.

Evans, R. D. (2001). Historical and contemporary distributions of aquatic mollusks in the Upper Connasauga River system of Georgia and Tennessee. M.S. Thesis, University of Tennessee Chattanooga, 277 p.

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

Gangloff, M. M. (2003). The status, physical habitat associations, and parasites of freshwater mussels in the upper Alabama River Drainage, Alabama. Ph.D. Dissertation, Auburn University.

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 3 July 2025.

Haag, Wendell R. (2009). Past and future patterns of freshwater mussel extinctions in North America during the Holocene, pp. 107-128. In: Turvey, Samuel T. (ed.). Holocene Extinctions. Oxford, UK & New York, USA: Oxford University Press. xii + 352 pp.

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

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

Hurd, J. C. (1974). Systematics and zoogeography of the unionacean mollusks of the Coosa RIver Drainage of Alabama, Georgia and Tennessee. Ph.D. Dissertation, Auburn University, 240 p.

Johnson, R. I. (1978). Systematics and zoogeography of Plagiola (= Dysnomia = Epioblasma), an almost extinct genus of freshwater mussels (Bivalvia: Unionidae) from middle North America. Bulletin of the Museum of Comparative Zoology 148: 239-321.

Lea, Isaac. (1859). Descriptions of twelve new species of uniones, from Georgia. Proceedings of the Academy of Natural Sciences of Philadelphia. 11:170-172. [after 28 June 1859; before 10 January 1860]

Lea, Isaac. (1870). A Synopsis of the Family of Naïades. Philadelphia: Henry C. Lea. 184 pp.

Lea, Isaac. (1874). Supplement to Isaac Lea's paper on Unionidæ. Journal of the Academy of Natural Sciences 8 [O. 13]: 55-69, pls. 19-22 (Obs. 13: 59-73).

Mirarchi, R. E., Garner, J. T., Mettee, M. F. and O'Neil, P. E. (2004). Alabama wildlife. Volume 2. Imperiled aquatic mollusks and fishes. University of Alabama Press, Tuscaloosa, Alabama. xii + 255 pp.

MolluscaBase eds. (2025). MolluscaBase. Epioblasma othcaloogensis (I. Lea, 1857). Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=857299 on 2025-07-03

NatureServe. (2014). NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed: January 29, 2015).

NatureServe. (2025). Epioblasma othcaloogensis: Southern Acornshell. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available at: https://explorer.natureserve.org/ [Accessed 3 July 2025]

Parmalee, P. W. and Bogan, Arthur E. (1998). The Freshwater Mussels of Tennessee. Knoxville, Tennessee: University of Tennessee Press. 328 pp.

Simpson, Charles Torrey. (1900). Synopsis of the naiades, or pearly fresh-water mussels. Proceedings of the United States National Museum 22(1205): 501-1044, pl. 18.

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.

Turgeon, D. D., Bogan, A. E., Coan, E. V., Emerson, W. K., Lyons, W. G. et al. (1988). Common and Scientific Names of Aquatic Invertebrates from the United States and Canada: Mollusks. American Fisheries Society Special Publication (16). 277 pp.

Turgeon, D. D., Quinn, J. F., Jr., Bogan, A. E., Coan, E. V., Hochberg, F. G., Lyons, W. G., Mikkelsen, P. M., Neves, R. J., Roper, C. F. E., Rosenberg, G., Roth, B., Scheltema, A., Thompson, F. G., Vecchione, M. and Williams, J. D. (1998). Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland: 526 pp.

U.S. Fish and Wildlife Service (USFWS). (1993). Endangered status for eight freshwater mussels and threatened status for three freshwater mussels in the Mobil River drainage. Final rule. Federal Register, 58(60): 14330-14340.

U.S. Fish and Wildlife Service (USFWS). (1997). Draft Recovery Plan for the Mobile River basin aquatic ecosystem. U.S. Fish and Wildlife Service, Southeast Region, Atlanta, Georgia.

U.S. Fish and Wildlife Service (USFWS). (2000). Recovery plan for the Mobile River basin aquatic ecosystem. U.S. Fish and Wildlife Service, Southeast Region, Atlanta, Georgia. 128 pp.

U.S. Fish and Wildlife Service (USFWS). (2003). Endangered and Threatened Widlife and plants; proposed designation of critical habitat for three threatened mussels and eight endangered mussels in the Mobile River basin; proposed rule. Federal Register 68(58): 14752-14832.

U.S. Fish and Wildlife Service (USFWS). (2004). Endangered and Threatened Widlife and plants; designation of critical habitat for three threatened mussels and eight endangered mussels in the Mobile River basin; final rule. Federal Register 69(126): 40083-40171.

U.S. Fish and Wildlife Service (USFWS). (2008). Fine-lined pocketbook (Hamiota (=Lampsilis) altilis), orange-nacre mucket (Hamiota (=Lampsilis) perovalis), Alabama moccasinshell (Medionidus acutissimus) Coosa moccasinshell (Medionidus parvulus), Southern clubshell (Pleurobema decisum), dark pigtoe (Pleurobema furvum), southern pigtoe (Pleurobema georgianum), ovate clubshell (Pleurobema perovatum), triangular kidneyshell (Ptychobranchus greenii), upland combshell (Epioblama metastriata), and southern acornshell (Epioblasma othcaloogensis), 5-Year Review: Summary and Evaluation. Jackson, MS. 37 pp.

U.S. Fish and Wildlife Service (USFWS). (2018). Upland Combshell (Epioblasma metastriata), Southern Acornshell (Epioblasma othcaloogensis). 5-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service, Southeast Region, Alabama Ecological Services Field Office, Daphne, Alabama. 15 pp.

U.S. Fish and Wildlife Service (USFWS). (2021). Removal of 23 Extinct Species From the Lists of Endangered and Threatened Wildlife and Plants. Proposed Rule. Federal Register 86(187): 54298-54338.

U.S. Fish and Wildlife Service (USFWS). (2023). Endangered and Threatened Wildlife and Plants; Removal of 21 Species From the List of Endangered and Threatened Wildlife. Final rule. Federal Register 88(199): 71644-71682.

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: 33-58.

Williams, James D., Bogan, Arthur E. and Garner, Jeffrey T. (2008). Freshwater mussels of Alabama and the Mobile Basin in Georgia, Mississippi and Tennessee. Tuscaloosa, Alabama: University of Alabama Press. xv + 908 pp.

Williams, James D. and Hughes, M. H. (1998). Freshwater mussels of selected reaches of the main channel rivers in the Coosa drainage of Georgia. U.S. Geological report to U.S. Army Corps of Engineers, Mobile District, Alabama. 21 pp.

Williams, James D., Warren, M. L., Cummings, Kevin S., Harris, J. L. and Neves, R. J. (1993). Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22. https://doi.org/10.1577/1548-8446(1993)018%3C0006:CSOFMO%3E2.0.CO;2

Wright, B. H. (1888). Check List of North American Unionidae and Other Fresh Water Bivalves. Portland, Oregon: Dorne & Cook, Printers. 8 pp. (un paginated).

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