Eunotia petasum Siver, Oddsund & Lott 2022, sp. nov.

• Main Authors: Siver, Peter A., Oddsund, Erik, Lott, Anne M.
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2022
• Subjects: Biodiversity; Taxonomy; Chromista; Ochrophyta; Bacillariophyceae; Eunotiales; Eunotiaceae; Eunotia; Eunotia petasum; Arctic
• Online Access: https://doi.org/10.5281/zenodo.7143248; http://treatment.plazi.org/id/9A71879BA34AFFB9FF30F9EDEC1AF9B2

Eunotia petasum Siver, Oddsund & Lott sp. nov . (LM Figs 15–21, SEM Figs 22–27) Description:— Valves are dorsi-ventral, elongate, widest in the middle of the valve, and becoming tapered and drawn out at the apices forming protracted ends (Figs 15–21). The ventral margin is concave, becoming slightly linear at the apices. The dorsal margin is more convex relative to the concave ventral margin such that the valve becomes progressively narrower from the center to the apices (Figs 24–27). Valves range in length from 19.6–57.6 µm with a mean of 38 µm, and in diameter at the valve center from 2.9–5.1 µm with a mean of 3.8 µm (n=25). At the apices, valve width ranges from 1.5–2.2 µm, with a mean of 1.8 µm. The margins of the valve face, especially along the ventral side, are slightly thickened and form right angles with the mantle (Figs 23–24). Striae are parallel, widely spaced with 13.5–19 per 10 µm, a mean of 16 µm, and consist of small, circular areolae that are opened on both the external and internal valve surfaces. Striae are continuous from the valve face onto the dorsal mantle, but may be interrupted and discontinuous with those on the ventral mantle (Figs 23–24). On smaller valves, the areolae on the ventral mantle may become more randomly spaced, especially below the raphe branches (Fig. 23). The mantle is shallow, approximately 1.5–2 µm, and the margin slightly thickened around each apex. The proximal end of the raphe commences near the middle of the mantle approximately 1/4 to 1/3 of the valve length from the apex, rises slowly on a linear path to the valve margin, and then bends up and onto the valve face terminating close to the end of the valve (Figs 23, 25). The proximal and distal raphe fissures both terminate as small round pores (Figs 23–25). On most specimens, the portion of the mantle below the raphe consists of short striae composed of a few pores, but on some valves the pores are randomly spaced and not organized into distinct striae. Internally, the distal raphe fissure terminates within a ...