Guide to Grunowia

Valves have an eccentric raphe, positioned on a keel. Striae are punctate. Fibulae are large and distinct.

The genus Grunowia was established by Rabenhorst (1864) to accommodate two species of nitzschioid diatoms with an undulate valve margin and dorsally connected fibulae extending half-valve, including Denticula sinuata Thwaites in W.Sm. and D. tabellaria Grunow. Subsequently, several other representatives of Bacillariaceae with an eccentric raphe and coarse fibulae were transferred to this genus or described within. 

Note, however, that available molecular data do not support reciprocal monophyly of Grunowia in relation to other genera within Bacillariaceae (Kociolek et al. 2025).

Grunowia is retained here to maintain consistency with historical data and until there is a better resolution of evolutionary relationships within Bacillariophyceae.