The genus Pinnularia contains some of the largest freshwater diatoms reaching up to almost half a millimeter.They commonly live benthic and epipelic in the mud of waters (im Schlamm der Gew(a)sser) as already Nitzsch, the describer of the type species wrote in 1816.Although Pinnularia is a large diatom genus for which more than 2000 taxa have been described, it has not been divided into smaller genera.In contrast, the genus Caloneis has been proposed to be synonymous because morphological features seem to be uniform.