Nupela potapovae

LM Morphology. Frustules solitary, isovalvar, narrow rectangular (< 2μm wide) in girdle view (Figs 5–7). Valves linear-lanceolate and dorsiventral, secondary side more arched than primary side, 20.9–24.0 μm long, 3.2–4.4 μm wide (Figs 1-4, 8-13). Apex capitate, about one-half width of valve at centre. Axial area narrow, lanceolate, widening gradually to the broad, asymmetrical, butterfly-shaped central area, which is wider on the secondary side. Central area distinguished by four refractive spots, one on each side of the proximal raphe endings. Raphe straight and complete on both valves, off-centre toward the primary side. External raphe fissures straight, distal endings hooked to the secondary side.Voigt faults on secondary side, evident on most valves (Figs 3, 11, white arrows). Occasionally, small circular depressions occur on the external valve surface (Figs 2, 4, black arrows). Striae are difficult to resolve in LM. SEM morphology. Central area bordered at valve margins by a single interrupted row of areolae (Figs 14–15, 19, 21). One or two isolated areolae in the central area may represent reduced transapical striae (Fig. 15). External proximal raphe endings terminate in small teardrop-shaped pores (Figs 14–15). Distal raphe fissures are hooked to the secondary side, where they extend down onto the apical mantle (Figs 14, 16–17). Internal raphe fissures straight, proximal endings bluntly pointed and bordered on each side by a shallow depression or pit, corresponding to the refractive spots in LM (Figs 21–23). One or two internal areolae openings are associated with, but not centred in, each pit (Fig. 23). Distal raphe fissures terminate in small helictoglossae, which are slightly deflected to the primary side (Fig. 20, black arrow). Striae radiate near the centre, becoming parallel then convergent at the ends, 42–46 in 10μm. Areolae composing the striae are typically arranged in three longitudinal rows on the primary side and four rows on the secondary side of the valve, plus one row along the valve mantle (Figs 14, 16). Longitudinal rows of areolae on the valve face decrease to one row at the narrowest part of the valve and then increase to two rows within the capitate ends (Figs 16–17). The istinction between valve and mantle becomes blurred at the rounded apices (Fig. 16). Areolae are oblong externally and elongate in the transverse axis (Figs 15–17). Externally, areolae appear as shallow oblong depressions, each with a much smaller and more circular internal opening (Figs 18, 22–23); hymenes were not observed.

• Author
  Bahls 2011
• Length Range
  20.9-24.0 µm
• Width
  3.2-4.4 µm
• Striae in 10µm
  42-46