Fragilaria pinnata var. subcapitata Frenguelli 1930

Vouilloud, Amelia A., Guerrero, José M. & Morales, Eduardo A., 2022, Fragilaria pinnata var. subcapitata Frenguelli, typification and current taxonomic status, Phytotaxa 566 (1), pp. 133-139 : 134-135

Fragilaria pinnata var. subcapitata Frenguelli 1930 . Revista Chilena de Historia Natural, Vol. 34, p. 199, figs 35, 4. Here Figs 1 –11.

Original description:— “ Difiere de todas las demás variedades de esta especie por sus contornos valvares estrechamente lanceolados, con extremos subcapitados, siendo ligada al tipo por formas de transición. Largo mm. 0,019 a 0,030, ancho mm. 0,006; estrías robustas, 7½ a 8 en mm. 0,01.” Freely translated as: It differs from the rest of the varieties by its narrowly lanceolate valve outline, with subcapitate apices, linked to the type through transitional forms. Length 19–30 µm, width 6 µm; striae robust, 7.5–8.0 in 10 µm (measurements converted from mm to µm by us).

Expanded description:— Valves heavily silicified, narrowly lanceolate with rostrate to subcapitate apices, more protracted in larger specimens, slightly heteropolar ( Figs 2–7 ). Sternum narrow, linear to lanceolate, sunken with respect to virgae in external view ( Figs 8–9 ). Striae uniseriate, parallel at valve center to slightly radial near apices, with typical ‘punch-hole’ appearance, continuous onto valve mantle ( Figs 10 –11). Striae at the same level as sternum in external view. Slit-like areolae, apically elongated, decreasing in size towards sternum and valve mantle ( Figs 8 –11). Volae hardly visible in external view, growing from internal part of vimines. Virgae somewhat wider than striae and elevated above sternum and striae ( Figs 9 , 11). Spines located on virgae, solid, and base occupies 2/3 of virgae width; body cylindrical with tips flattened and forked ( Figs 10 –11, arrowheads). Spines present at valve poles. Apical pore fields present at both poles, modest, formed of few round pores (Fig. 11, arrow).

Morphometric data: Length 16.0–21.5 µm; width 3.5–4.0 µm; length:width 4.8–5.2; 10–12 striae in 10 µm; 60–70 areolae in 10 µm.

Type:— CHILE, Antofagasta Province, Calama: Calama Looser, diatomite. Frenguelli Collection , unknown date, (Lectotype designated here S/ N Slide N °4! England finder L/46 = Fig. 2 ) .

Figures

FIGURES 1–10. Fragilaria pinnata var.subcapitata Frenguelli from the Calama diatomitetype material.1. Original drawing of Frenguelli (1930, p. 198, fig. 4). 2–10. Specimens from type population. Figs 2-7. LM. Specimens in valve view. Fig. 2. Lectotype. Figs 8–11. SEM. Specimens in external valve views. Figs 8–9. Whole frustules. Figs 10–11. Details of the apices, note the small pore field (arrow in Fig. 11) and spines with tips flattened and forked (arrowheads). Scale bars: 10 µm (Figs 2–7), 5 µm (Figs 8, 9), 1 µm (Figs 10, 11).