Fottea X:X | DOI: 10.5507/fot.2025.011

Revision of the genus Stauroforma (Staurosiraceae, Bacillariophyceae) based on varieties of Fragilaria virescens described by Albert Grunow

Bart Van de Vijver1, 2, Tanja M. Schuster3, David M. Williams4, Wolf-Henning Kusber5
1 Meise Botanic Garden, Research Department, Nieuwelaan 38, 1860 Meise, Belgium
2 University of Antwerp, Department of Biology - ECOSPHERE, Universiteitsplein 1, B-2610 Wilrijk, Belgium
3 Natural History Museum, Department of Botany, Herbarium, Burgring 7, 1010 Vienna, Austria
4 Natural History Museum, Department of Life Sciences, Cromwell Road, London, SW7 5BD, UK
5 Botanischer Garten und Botanisches Museum Berlin, Freie Universität Berlin, Königin-Luise- Straße 6-8, 14195, Berlin, Germany

A revision of the genus Stauroforma is proposed based on the analysis of several historic slides prepared by Grunow to describe Fragilaria virescens var. exigua. The original materials are analysed using both light and scanning electron microscopy together with a critical examination of the original drawings and notes Grunow made on his new taxa. Based on this, the genus description of Stauroforma is emended and the morphological descriptions of S. exiguiformis and S. inermis are updated. Grunow's variety subsalina is raised to species level as Stauroforma subsalina. A new species, Stauroforma subcassubica is described splitting it from S. cassubica, the latter having larger valves. The results of this revision will enable a more exact identification of the different Stauroforma species observed in freshwater and brackish water bodies in Europe.

Keywords: Historical Material; Morphology; New Combinations; New Species; Revision; Stauroforma

Received: May 28, 2025; Revised: August 27, 2025; Accepted: September 11, 2025; Prepublished online: September 23, 2025 

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