Vitinellopsis nov. gen., a new calcareous alga (Chlorophyta, Bryopsidales) from the Silurian of Gotland (Sweden), and the tribe Vitinelleae nov. nom

The algal genus Vitinellopsis nov. gen. is well represented in the Silurian limestones of Gotland (Sweden). This new taxon is interpreted as a calcified codiacean alga (Chlorophyta, Bryopsidales). In the studied material, the calcareous wall of sparry calcite, probably originally aragonitic, appears well preserved. The subcylindrical thallus, with rounded ends, rarely bifurcated, measures up to 27 mm long and 2.5 mm wide. The medullar zone exhibits 4-6 longitudinal, subtly undulating siphons; the subcortical zone shows inflated, vesiculiform radial siphons, and the cortical zone displays small, relatively short acrophorous siphons. The status of the tribe Vitinelleae nomen novum, formerly Bothryelleae, is discussed. Given its abundance, ease of identification, and short stratigraphic range, Vitinellopsis gotlandica nov. gen., nov. sp. may prove useful for regional correlations, facies and paleobiogeographic studies.