Synonyms: Pleurobema (Sintoxia) riddellii, Quadrula (Fusconaia) friersoni

Distribution: This species is rare across its distribution, and it known from streams in east Texas, east Oklahoma, the Ouachita River system in Arkansas, central Louisiana, and was recently confirmed in the Pearl River in eastern Mississippi (Johnson et al. 2023). In Oklahoma, this species is likely restricted to the lower Red River drainage, specifically the Little River system. In the Ouachita River system in Arkansas, recent studies have suggested that these populations are phylogenetically distinct from Texas, Oklahoma, Louisiana, and Mississippi populations (Inoue et al. 2018) (Johnson et al. 2023).

Life History and Ecology: Occurs mainly in medium-sized rivers on firm substrate of coarse gravel and sand. Fish hosts for this species remain to be confirmed but given that ecological hosts for other Pleurobema species are believed to be restricted to minnows (family Leuciscidae), it is likely that P. riddellii is a minnow specialist. Several other mussel species such as Pustulosa pustulosa, Fusconaia askewi, F. chunii, and F. flava can be easily misidentified as P. riddellii (and vice versa) when identified by shell morphology alone.

Special Status: Under Review (Proposed Threatened)

Shell Description: click here for shell description

Literature cited:

Inoue, K., Hayes, D. M., Harris, J. L., Johnson, N. A., Morrison, C. L., Eackles, M. S., ... & Randklev, C. R. (2018). The Pleurobemini (Bivalvia: Unionida) revisited: molecular species delineation using a mitochondrial DNA gene reveals multiple conspecifics and undescribed species. Invertebrate Systematics, 32(3), 689-702.

Johnson, N. A., Beaver, C. E., Kiser, A. H., Duplessis, M. A., Wagner, M. D., Ellwanger, R. J., ... & Smith, C. H. (2023). Molecular data validate historical and contemporary distributions of Pleurobema riddellii (Bivalvia: Unionidae) and help guide conservation and recovery efforts. Endangered Species Research, 52, 1-15.