Abstract
Eunotia elliotii sp. nov. is described from an unnamed tributary of the headwaters of the Bondo River in the Republic of the Congo. The diatom community in which it was found was dominated by several other species of Eunotia with several other taxa co-occurring including Actinella, Humidophila, Luticola, Nupela, Gomphonema, Brachysira, Sellaphora, Navicula, Frustulia, Orthoseira and Pinnularia. The morphological features of the new species are studied using light and scanning electron microscopy. Eunotia elliotii can easily be distinguished from other Eunotia species by its typical valve outline with two dorsal undulations, protracted rounded apices, unevenly spaced striae and the irregular thickened silica wall, which is clearly visible under the light microscope. Under scanning electron microscopy the valve face is unevenly corrugated with striae recessed in the troughs of the corrugations. Externally, surrounding the striae, the troughs are filled with numerous small round depressions in the valve face, such structures have not been observed before in Eunotia. This taxon also has no discernable rimoportula present. Differences between the new species and morphologically related species such as Eunotia rudis and Eunotia pierrefuseyi described from the Democratic Republic of the Congo and several other similar taxa are discussed.
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