Jahn R., Mora D., Abarca N., Kusber W.H., Zimmermann J., Skibbe O.
Nova Hedwigia, vol. 120, n° 1-4, pp. 263-285, 2025
Cocconeis witkowskii sp. nov. from tidal flats of the Eastern North Sea is described as new with morphological and molecular data. It is compared morphologically to the currently most closely related taxon as based on molecular data, the epiphytic Cocconeis euglypta, from the Southern Baltic Sea for which new strains are analyzed. The morphology of Cocconeis witkowskii sp. nov. is also compared to Cocconeis neothumensis var. marina, a species described from Mediterranean habitats, and to some other taxa. Besides its typical heterovalvy with a strongly silicified sternum valve, an only slightly silicified raphe valve, and a rudimentary hemi-fascia on both valves, the submarginal ring of Cocconeis witkowskii is inconspicuous. Additionally, the valvocopula of the raphe valve is closed and has no fimbriae, whereas the valvocopula of the sternum valve is open at both apices and has smooth but undulating edges.
