Phylum: Charophyta   Family: Desmidiaceae

Cosmarium papillatum (D.B. Williamson) F.A.C. Kouwets 2025

First described in 1997 as C. repandum var. papillatum, from a slightly acidic roadside pool near Forsinard, north-east Sutherland, Scotland. It has since been established that it has little in common with C. repandum and has been elevated to species level. This current find is thought to be the second example. The semicell sides are slightly divergent and support one or two intramarginal granules, it also has a small central protuberance. Similar to the equally rare C. lapponicum but with noticeably more convex apices.
Single cell dimensions: L: 21.9 µm; B: 20.4 µm; Is: 9.3 µm; Th: c.12.5 µm; L/B: 1.08.
Little is known about its geographical range, but a third record has come from Sweden possibly suggesting an Atlantic distribution. It would seem to like slightly acidic moorland pools.

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