Stauroneis thermicola

Valves are linear-lanceolate with protracted, subrostrate to capitate rounded ends. A narrow rectangular stauros is present. Striae adjacent to the stauros are parallel, and the rest are curved and radiate throughout the valve, increasing in density from mid-valve to apex. Axial area very narrow, expanding slightly at the central area. The raphe is straight and filiform, with inflated proximal ends. Areolae are coarse near the raphe at mid-valve, but otherwise not visible in LM.

In 2011, Hoffmann et al. took issue with the use of the names Stauroneis thermicola and S. parathermicola for valves in this group exhibiting variability in apical constriction. The authors note that differences in this feature are consistent, and propose the two morphologies be treated interspecifically, not intraspecifically, as has been the case for some time. However, given that the authors cite no evidence for this fact, and several USGS regional stream surveys in the United states have found these morphotypes to co-occur (personal observation), their claim of heterospecificity, at least in North America, is not currently well supported. This page takes a conservative approach until the morphologically variable taxon is further investigated.