Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pseudoquadratum F.A.C. Kouwets 2025

This recently described species was part of the Cosmarium quadratum Ralfs 1848 complex. It’s similar in size to that species but is mainly distinguished by its wide-open sinus.
Cell dimensions: L: 57-58 µm; B: 32.8-34.2 µm; Is: 21.4-32.3 µm; Th: c.28 µm; L/B: 1.68-1.76.
Because of the foregoing the status is uncertain. From the little data available it would seem to prefer circumneutral waters such as disused peat-cutting and loch-margins.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.