Descriptions of a new species and a new subspecies of freshwater mussels, Epioblasma ahlstedti and Epioblasma florentina aureola (Bivalvia: Unionidae), in the Tennessee River drainage, USA

A new species and a new subspecies of Epioblasma are described from the Tennessee River drainage, USA. Epioblasma ahlstedti (Duck River Dartersnapper) currently is restricted to the Duck River in west-central Tennessee (TN). However, museum collections indicate that the species likely occurred in the Buffalo River, TN, a tributary to the Duck River, and in the Tennessee River at Muscle Shoals, Alabama (AL), and lower Shoal Creek, AL. The following diagnostic morphological characteristics of E. ahlstedti are based on the female: (1) pronounced posterior-ventral shell expansion of the adult female, shell; (2) slate-gray to dark-purple mantle-pad; (3) spoor texture of the mantle-pad; and (4) display of a single, tan-colored micro-lure that moves slowly side-to-side. Epioblasma florentina aureola (Golden Riffleshell) currently is restricted to Indian Creek, a tributary to the upper Clinch River, Virginia. Historically, the species occurred in numerous tributaries in the Tennessee River drainage downstream at least to the Duck River. The following diagnostic morphological characteristics of E. florentina aureola are based on the female: (1) gray mantle-pad with a black mottled background; and (2) mantle-pad is pustuled but the pustules are rounded. The genus Epioblasma represents the most endangered group of freshwater mussels in North America; 18 of the recognized 25 species or subspecies are already extinct. Likewise, these newly described species and subspecies are critically endangered and despite being listed as endangered under the Endangered Species Act remain in need of focused conservation to prevent their extinction.