Guide to Rexlowea

Rexlowea was recently described based on Placoneis navicularis (Ehrenb.) Cox 2003. At present the genus is monotypic.

The valves are large (up to approx. 130 µm in length). The axial area is narrow and straight, with a small central area. The raphe is lateral and undulate. External proximal ends are dilated, while the distal ends are deflected. The striae are radiate. Near the central area, the striae are composed of large, round areolae. Near the apices, the striae are biseriate. Both septa and pseudosepta are present.

Rexlowea differs from Placoneis by a number of features, including absence of stigmata and presence of septa and pseudosepta. The genus is suggested to share affinities with gomphonemoid diatoms (Kociolek and Thomas 2010, Kociolek and Stoermer 1998) and may be allied with Brebissonia.