Cyclotella Guide
Credit: Kalina Manoylov
  1. Valve face with differential ornamentation between central and marginal area
  2. Central area flat to tangentially undulate
  3. Single rimoportula positioned on mantle costa

In the genus Cyclotella sensu stricto the rimoportula is positioned on a costa, within the ring of marginal fultoportulae (Alverson et al. 2011).

Like the genera Cyclostephanos, Discostella and Lindavia the valve face of Cyclotella has differential ornamentation between the central and marginal areas. The central area of the valve face may be flat to tangentially undulate and smooth to colliculate. Numerous marginal fultoportulae are present.

Cyclostephanos, Discostella and Lindavia have been separated from this formerly broad group of diatoms. Still, features within the remaining species in Cyclotella are variable, indicating that the genus may continue to be an unnatural group. That is, Cyclotella is not an evolutionary lineage, but represents a mixed grouping of taxa.