Navicula rumaniensis Hust. ex Simonsen (1987: 165

Wojtal, Agata Z., Ognjanova-Rumenova, Nadja, Buczkó, Krisztina, Siwek, Janusz & Vijver, Bart Van De, 2015, Revision of Navicula striolata (Grunow) Lange-Bertalot and N. rumaniensis Hustedt with the description of N. friedelhinziae sp. nov., Phytotaxa 204 (3), pp. 177-192 : 183-184

Navicula rumaniensis Hust. ex Simonsen (1987: 165 , plate 265, figs. 7, 8) ( Figs. 29 44 )

Validating description:— “ Valvae anguste lanceolatae, apicibus late roundatis, non protractis, circiter 60 um longae, 12 um latae ” ( Simonsen 1987).

Type:— ROMANIA. “fossils”. BRM! Hustedt Collection, holotype designated by Simonsen X7/34.

LM:— ( Figs. 30–33 ): Valves lanceolate with convex margins, a rather gibbous valve center gradually tapering towards the broadly rounded, non-protracted apices. Largest valves more or less elongated at the 2/3 length between the valve centre and the apices. Valve dimensions (n=30): length 61–76 μm, width 10.5–14.0 μm. Axial area rather broad, linear-lanceolate, gradually widening towards the central area. Central area transversely widened, distinctly bordered by irregularly shortened striae alternating with longer striae. Raphe distinctly lateral. Proximal raphe endings clearly drop-like expanded, deflected towards the secondary valve side. Distal raphe endings hardly discernible in LM. Transapical striae distinctly radiate in the mid-valve becoming parallel and slightly convergent towards the apices, 8–10 in 10 μm. Lineolae clearly discernible, 24–26 in 10 μm.

SEM:— ( Figs. 34–44 ): Raphe sternum elevated through most of the valve becoming confluent towards the apices. Irregular, elongated ridges present in the axial area, extending from the central area almost up to the valve apices. Ridges more densely present near the central area. External proximal raphe endings undulating, becoming clearly droplike expanded and forked with a fine silicate tongue, entering the raphe fissure. External distal raphe fissures clearly deflected, extending as narrow fissures onto the valve apex margins. Striae continuing without interruption onto the valve mantle. Lineolae longer near the valve apices, shorter or of equal length as the virgae, becoming clearly shorter than the virgae near the central area. Striae continuing almost entirely up to the valve apices, leaving only a very short hyaline area on each apex ( Figs. 41 – 43 ). Externally, elongated ridges, similar to the ones in the axial area, present on the valve mantle. Internally, raphe branches very narrow, straight, running on the side of a thickened, raised sternum. Proximal raphe endings simple, located on a small, elevated central nodule ( Figs. 34–36 ). A pronounced accessory rib running apically along the whole valve excluding the central nodule. Distal raphe endings terminating in small helictoglossae ( Figs. 37, 39 ). Pseudosepta clearly present, marked by the presence of one, occasionally two, large pore(s). Virgae clearly raised, bordering the striae, the latter running in shallow grooves.

Figures

FIGURES 29–33. Navicula rumaniensis Hust. 29. Reproduction of the original drawing in Schmidt’ Atlas. 30–33. LM photographs of valves from Hustedt Collection and Pantocsek Collection. 30. Slide N17/27 unnamed, marked by Hustedt specimen (slides in Hustedt collection have only his description—Fossils, Rumänien; no slide has the name with N. rumaniensis). 31 a, b. The same valve at different focus from the slide X7/34—mentioned by Simonsen (1987) as with marked specimen—Holotype slide. Scale bar = 10 μm.

FIGURES 34–39. Navicula rumaniensis Hust. 34, 35. SEM internal images of the valve from Hustedt Collection—E8338 Rumänien 8, in oblique and straight position. 37, 39. Internal images of small helictoglossae and pseudosepta. 38. External distal raphe fissure deflected, extending as narrow fissures onto the valve apex margins. 37, 38. Hustedt Collection, E8338 Rumänien 8. 39. Valve from Pantocsek Collection. Scale bars: 34, 36 = 20 μm; 37, 39 = 5 μm; 38 = 2 μm.

FIGURES 40–44. Navicula rumaniensis Hust., SEM. 41–44. External view of the frustule in oblique (41) and straight position (42–44) with details of central and apical frustules parts. 40–44. Valves from Pantocsek Collection. Scale bars: 40 = 25 μm; 41, 42 = 20 μm; 43, 44 = 5 μm.