Staurosirella neopinnata

Staurosirella neopinnata sp. nov. Observations (Figs 1–12 (LM), 13–24 (SEM)):—Frustules rectangular in girdle view (Figs 2, 12), joined together by interlocking spines (Figs 2, 24). Valves elliptical, most frequently isopolar to rarely slightly heteropolar (Figs 10, 11, 14, 15). Abvalvar edge of mantle parallel to valve face-mantle junction (Figs 18, 20–24). Axial area narrowly lanceolate (e.g. Figs 1–12), giving sometimes the impression of having a zig-zag shape due to its raised feature exacerbated by raised virgae (e.g. Fig. 8). Virgae doubly flared, opening up toward the axial area and on the mantle (Figs 14, 15, 20–24). Internally, axial area and virgae are also raised leaving the striae in depressions (see Fig. 53 from a different depth along the same core). Vimines long and narrow becoming longer toward the valve face border (Figs 14, 15). Striae running uninterrupted from valve face to mantle. Volae small and projected towards the valve interior, arising from the longest side of the vimines (Figs 14, 15). Spines originating from two (rarely three) points on each virgae at the valve face-mantle junction, initially hollow then becoming an apically elongated structure with a lamina that becomes spatulate in shape at the top (Figs 14, 15, 19, 22, 23). Apical pore fields located on the valve mantle, reaching the valve face-mantle junction at the polar nodules and isolated from neighboring striae, usually equally developed on both valve poles and less prominent in smaller valves (Figs 14, 15, 19). Girdle elements variable in number, open, lacking pores, ligulated, and with valvocopula being much larger (Figs 16, 18, 21–24). The latter bears well developed fimbriae (not shown for the type). Dimensions (n>100):—Length 4–25 µm; width 4.0–4.7 µm; striae 8.0–9.5 per 10 µm. Type:—SCOTLAND. Loch Borralan, at 208 cm depth in a 4.3 m core of sediment. Sutherland, Fionn Loch drainage system (Haworth 1976). Age of sediments: Flandrian, approximately 10226 +/- 190 YBP (Slide BR-4557). Partially illustrated here in Figs 1–12 (LM) and 13–24 (SEM). Taxonomic remarks:—All the populations found in late-glacial sediment from both lochs are similar to each other. Some valves more heteropolar, slightly clavate, could also be found in Borralan at 150 cm sediment depth (Fig. 37). The dimensions compiled from all the sections studied from both cores are length 4–36 µm; width 3.3–5.3 µm; striae 7.0–9.5 per 10 µm. The fimbriae of the valvocopula were observed in several specimens in sections other that the one used for the type (Figs 54, 146, 153, 187). This species lacks an apical depression (step), viminules and any blister-like depositions on the abvalvar edge of the mantle.

• Author
  E.A.Morales 2019
• Length Range
  4-36 µm
• Width
  3.3-5.3 µm
• Striae in 10µm
  7-9.5