Eunotia luna var. aequalis f. major Frenguelli

Guerrero, José M. & Vouilloud, Amelia A., 2022, Taxonomic revision of Eunotia luna var. aequalis f. paucistriata Frenguelli and E. luna var. aequalis f. major Frenguelli: analysis of type material, lectotypification and current taxonomic status, Phytotaxa 561 (3), pp. 291-300 : 295

Eunotia luna var. aequalis f. major Frenguelli ( Figs 27–36 )

According to the original description ( Frenguelli 1933), E. luna var. aequalis f. major differs from E. luna var. aequalis by its longer valves, with striae somewhat irregularly distributed. The valve illustrated by the author (here reproduced in Fig. 27 ) is elongated, with parallel margins and broadly cuneate, ventrally deflected apices. Striae are parallel and become more densely spaced at the apices, where they flank the terminal nodule (see Table 1 for morphometric data). The specimens from the original material observed with LM ( Figs 28–33 ) fit rather well the original description of this form, although valve dimensions are lower than those reported by the author whereas stria densities are higher than originally reported, this difference being more marked for mid valve striae ( Table 1 ). Additionally, most specimens exhibit short dorsal striae variably extending onto the valve face ( Figs 28, 30–31, 33–34 ), which were not depicted in the original illustration.

Under SEM ( Figs 34–36 ) we only found one valve of this form, in internal view and slightly tilted positioned, with the closed valvocopula attached. Internal areola openings are round and are located in narrow troughs ( Fig. 35 ). Due to the presence of detrital material that partially covers the valve, no details are visible regarding the internal raphe fissure and the presence of rimoportulae. The portion of the mantle visible shows the filiform raphe with its simple proximal end ( Fig. 36 ). The areolation pattern between the raphe and the valve margin is denser and more disorganized than in the rest of the mantle ( Fig. 36 ).

Figures

FIGURES 27–36. Eunotia luna var. aequalis f. major Frenguelli. 27. Original drawing of Frenguelli. 28–33. LM. Size diminution series. 34–36. SEM. Internal views. 34. General view of a tilted valve. 35. Detail of valve center showing the arrangement of striae. 36. Detail of the valve apex showing mantle areolation pattern in external view; note the raphe on the mantle in external view. 28–29. Specimen from Series 264. 30–36. Specimens from Series 265. 32. Lectotype of E. luna var. aequalis f. major. Scale bar = 10 µm (Figs 27–34), 5 µm (Figs 35–36).