Olifantiella elisabethiana, a new raphid diatom species (Bacillariophyta) observed in the Port of Antwerp (Belgium)

During an extensive analysis of the diatom flora of the Port of Antwerp ( Belgium) in 2008, an unknown naviculoid taxon was observed. Detailed morphological investigations using light, scanning electron and transmission electron microscopy resulted in the description of this unknown taxon as Olifantiella elisabethiana Van de Vijver sp. nov. This new small-celled, biraphid species is characterized in having a typical internal process named buciniportula, opening externally by a pore or slit, unseriate striae composed of one single transapically elongated areola and a siliceous hymenous velum extending internally from the valve mantle to halfway the valve margin and the axial area. The morphological observations allowed to precise the characterization of the genus Olifantiella. A modification of the original description is proposed with regard to the internal structure. The presence of this Olifantiella species in the northern hemisphere is briefly discussed as all other known taxa of this genus have only been found in the tropical coastal waters of the Indian and Pacific Ocean.