Grunowia mannii Kociolek & Danz, 2022

Kociolek, J. P. & Danz, A., 2022, Taxonomy and valve ultrastructure of new and interesting freshwater fossil diatoms (Bacillariophyta) of Miocene age from the Espanola Formation of New Mexico, U. S. A. II. Description of a New Grunowia species with comments on the genus, Phytotaxa 530 (3), pp. 295-300 : 298

Grunowia mannii Kociolek & Danz , sp. nov., Figures 1–15 .

Description:— Valves narrowly cruciform, with apical axis very narrow and apices narrow, round; the center with rounded margins. Length 5 – 16 µm, breadth 2 – 6 µm. Keel distinct, placed at or near the center of the valve. Fibulae 8 – 10/10 µm. Striae fine, appearing as lines (without visible puncta), parallel, 18 – 23 / 10 µm. Number of specimens measured = 100.

In the SEM, the valve exterior has a narrow, raised keel positioned just off-center in larger ( Figs 8, 9 ) specimens but closer to the margin in smaller specimens. Striae are composed of round areolae, 40 – 50 in 10 µm within a stria. Striae are parallel with a density of 20 – 25 in 10 µm. Number of specimens measured = 10. The raphe is positioned in the keel, and has two distinct branches ( Figs 8, 11 ). External distal raphe ends are bent slightly and curved onto the narrow mantle ( Fig. 10 ). External proximal raphe ends terminate close to one another and are straight ( Fig. 11 ).

Internally, the raphe is contained in a canal, with portules of varying sizes ( Figs 12 – 14 ). Fibulae are relatively wide for the size of the valves. The proximal raphe ends terminate at a small central nodule that appears similar to helictoglossae ( Fig. 15 ).

Type:— USA, Rio Arriba County, New Mexico, Chamita Formation, USGS Diatom Locality 4672, holotype COLO! Slide # 278018 in the J.P. Kociolek Diatom Collection at the University of Colorado, Boulder = Fig. 4 ; isotype: ANSP! Slide #GC 65441 in the Academy of Natural Sciences of Drexel University .

Etymology:— Named for the diatomist Dr. David Mann, for all of his efforts to uncover and resolve the riddles contained within the Bacillariales .

Comments:— This delicate species was well-preserved in the ca. 9 million year-old sediments of the Esmeralda Formation.

Figures

FIGURES 1–7. Grunowia mannii Kociolek & Danz sp. nov. LM. Size diminution series. Fig. 1 represents an initial valve. The holotype is presented in fig. 4. Scale bar = 10 µm.

FIGURES 8–11. Grunowia mannii Kociolek & Danz sp. nov. SEM of valve exterior. 8, 9. Valve view showing characteristic shape and distinctly-elevated, raphe-bearing keel. 10. Apex of the valve showing raphe end extending onto the mantle. 11. Central portion of the valve, with raphe branches interrupted. Scale bars = 5 µm (Figs 8, 9), 3 µm (Fig. 10), 2 µm (Fig. 11).

FIGURES 12–15. Grunowia mannii Kociolek & Danz sp. nov. SEM. Valve interior. 12–14. Entire valves, showing differences in valve shape relative to length. Large fibulae and large portules over the raphe canal are evident. 15. View of central nodule showing small, helictoglossa-like center and discontinuous raphe branch. Scale bars = 5 µm (Fig. 12), 4 µm (Fig. 13), 3 µm (Fig. 14), 1 µm (Fig. 15).