Distrionella coxiana, a new fragilarioid diatom species (Bacillariophyceae) from Tierra del Fuego, Patagonia, Argentina

Background and aims - A few years ago. a new survey started of the freshwater diatom flora from peatbogs of Tierra del Fuego (southern Argentina). During this survey, an unknown fragilarioid diatom belonging to the genus Distrionella that could not be identified using the currently available literature was discovered. Methods - Using both Light Microscopical and Scanning Electron Microscopical techniques, the morphology of the unknown Distrionella species has been analysed. The new taxon is properly described, illustrated and compared with all other possible similar Distrionella taxa. known worldwide. Key results - Distrionella coxiana possesses a unique combination of morphological features that excludes conspecificity with all other members of the genus: it is characterized in having narrow, linear valves with small, capitate apices. Transapical ribs, a typical feature of the genus Distrionella, are only weakly developed. One rimoportula is observed close to the apices. Both apices have well-developed apical porefields. The girdle bands bear one complete row of poroids often accompanied by a second, incomplete row of small poroids. Notes on the occurrence and ecology of the new taxon are added.