Diagnosis_Species: The strain GeoB 427 exhibited both motile thecate cells and immotile calcareous coccoid cells. The motile cells were predominant, whereas the coccoid cells were rare. The epitheca was conical (the outline sometimes slightly polygonal) and had a slightly acuminate, hyaline apex, while the hypotheca’s outline was polygonal through hemispheric. In apical view, the cingular outline was nearly circular through slightly polygonal. The cingular girdle was excavated and slightly descendent, the displacement comprised always less than 50% of the cingulum width. The sulcus was likewise excavated and extended from the cingulum to the antapex.The basic thecal plate arrangement was Po, cp, X, 4’, 3a, 7”, 6c, 5s, 5’’’, 2’’’’. Aberrant formulas were frequently observed. The cell surface was smooth and did not show any ornamentation. Small circular pores were irregularly scattered over the thecal plates or rarely linearly arranged near the plate boundaries. The apical pore complex was elongated. The apical pore consisted of a circular apical pore plate and was shielded by a cover plate. A canal (or X or preapical) plate was also present. Partitions of the apical collar were not observed. The sulcal region was composed of five plates, which varied slightly among individuals in size and shape. The smaller sulcal plates, Sa and Sm, were mostly covered by the larger plates, Sd and Ss. Along the boundaries of the thecal plates, the overlap of adjacent plates was visible occasionally by growth bands. Generally, it followed an imbricate pattern from dorsal to ventral: In the epitheca, the dorsal precingular plate 4” was the keystone plate, as was plate 4C in the cingulum. The keystone plate of the hypotheca was postcingular plate 3”’, and the antapical plates laid under the postcingular plates. The large sulcal plate Sp was overlapped by all adjacent plates. Cell division is normally by eleuteroschisis. Thecate cells opened along the upper ridge of the cingulum (i.e., the cingulum was attached to the hypotheca) for releasing dividing or ecdysing cells.
The thecate cells were variable in size and could be classified into three different dimension types. The cells of the small-sized type ranged from 17–23 μm in length (mean: 21 μm; median: 22 μm; SD: 2 μm; n=17) and 14–20 μm in width (mean: 17 μm; median: 16 μm; SD: 2 μm; n= 17) and were light yellow in colour. The majority of the motile cells in the cultivation plates represented the mid-sized dimension type. Such cells ranged from 25–37 μm in length (mean: 32 μm; median: 32 μm; SD: 3 μm; n=101) and 17–27 μm in width (mean: 22 μm; median: 22 μm; SD: 2 μm; n=101). The colour of this cell type was yellowish through golden. The cells of the large dimension type ranged from 39–44 μm in length (mean: 40 μm; median: 40 μm; SD: 2 μm; n=18) and 23–29 μm in width (mean: 25 μm; median: 25 μm; SD: 2 μm; n=18). The colour of the large-sized cells did not differ from the colour of the mid-sized cells.

The immotile coccoid cells were spherical to mostly ovoid. They were variable in size ranging from (including the processes) 34–56 μm in length (mean: 46 μm; median: 46 μm; SD: 5 μm; n=86) and 30–44 μm in width (mean: 37; median: 38 μm; SD: 3 μm; n=86). During the coccoid stage, a red accumulation body was visible. The outer calcareous layer of the cells was composed of numerous processes. The processes were styliform and narrowly conoid through narrowly pyramidal with a tringular base and varied in length (ranging from 2–5 μm), width and shape (Fig. 3F–G, J–M). The apex of the processes was obtuse or capitate and varied in the same strain at the same moment in time.

Body_smallsize_length: 17–23 μm
Body_smallsize_width: 14–20 μm
Body_midsize_length: 25–37 μm
Body_midsize_width: 17–27
Body_largesize_length: 39–44 μm
Body_largesize_width: 23–29 μm
Body_restingcyst_length: 34–56 μm
Body_restingcyst_width: 30–44 μm
Sequence_ITS: JN982383