Bourrellyodesmus constrictus (Kurt Förster) G.J.P.Ramos, C.E.M.Bicudo & C.W.N.Moura 2022

Ramos, Geraldo José Peixoto, 2022, Nomenclatural and taxonomic notes on Brazilian desmids IV, Notulae Algarum 224, pp. 1-7 : 1-2

Bourrellyodesmus constrictus (Kurt Förster) G.J.P.Ramos, C.E.M.Bicudo & C.W.N.Moura , comb. nov. et stat. nov.

Basionym: Xanthidium tenuissimum var. constrictum Kurt Förster, Algological Studies / Archiv für Hydrobiologie, Supplement 28: 233. 1981.

Note: “ Xanthidium tenuissimum var. constrictum ” Kurt Förster (1974: 165, pl. 8: figs 13, 14) is invalid as two collection localities were mentioned in the protologue (“Rio Maués-mirim” [15.11.1959] and “Rio Maués-assú” [15.11.1959], both in the State of Amazonas, northern Brazil), the name is thus not based on a single gathering (Art. 40.2) and a nomenclatural type was not designated at that time (ICN Art. 40.1). Förster (1981: 233) validated the name by selecting Förster (1974: pl. 8: fig. 8) as the holotype (“ikonotypus”) of the validated name.

The second group comprises the Xanthidium taxa that have Cosmarium -like morphology. We do not consider them members of genus Xanthidium because the spines are not confined to the cell angles, instead developing two superimposed series on each side of the semicell rather than continually along the margins.

The Brazilian taxa of Xanthidium under discussion were proposed by Kurt Förster based on material gathered in the central ( Förster 1964) and northern regions ( Förster 1963). There are other species of Cosmarium like Xanthidium representatives such as C. horridum Borge (1899: 23) , and C. paraguayense Borge (1903: 88) , both of which are endemic to South America.

However, Xanthidium obsoletum var. brasiliense Grönblad (1945: 22 , fig. 158), another taxon based on material gathered in northern Brazil, is clearly related to Cosmarium . Nevertheless, we do not consider the information from the original description sufficient to propose a new combination for this taxon, as it resembles underdeveloped forms of other species such as Cosmarium paraguayense O.Borge ( Borge 1903: 88, pl. 2: fig. 16) or C. guatemalense W.R.Taylor ( Taylor 1939: 117, fig. 1: 1–3). Further studies, preferably at a populational level, are recommended to investigate this taxon as Grönblad included only dimensions from a unique cell that was illustrated only in front view.

Additionally, there is a species originally proposed by Croasdale & Grönblad in Scott & al. (1965) from the Amazon basin, which was renamed subsequently by Croasdale (1971) as Xanthidium echinatum .