Cosmarium decedens var. scrobiculatum (Kurt Förster & Eckert) G.J.P.Ramos & C.W.N.Moura 2022

Ramos, Geraldo José Peixoto, 2022, Nomenclatural and taxonomic notes on Brazilian desmids IV, Notulae Algarum 224, pp. 1-7 : 3

Cosmarium decedens var. scrobiculatum (Kurt Förster & Eckert) G.J.P.Ramos & C.W.N.Moura , comb. nov. et stat. nov.

Basionym: Cosmarium sublobatum [ var. brasiliense ] f. scrobiculatum Kurt Förster & F.Eckert in Förster, Hydrobiologia 23: 405, pl. 20: fig. 9; pl. 46: fig. 9. 1964.

Note: Förster & Eckert in Forster (1964) proposed Cosmarium sublobatum var. brasiliense f. scrobiculatum based on material collected from “Rio das Femmeas, Goyaz” (currently Tocantins State), central Brazil. Although Cosmarium sublobatum var. brasiliense is currently the basionym of Euastrum sublobatum var. brasiliense , the f. scrobiculatum has cells morphologically closer to Cosmarium decedens , particularly to var. sinuosum (P.Lundell) Raciborski. The main diagnostic feature of the Brazilian material is the presence of a scrobicule in the mid-region of each semicell. We thus propose to transfer this forma to Cosmarium decedens , but at the varietal level.