Anorthoneis hummii Hustedt 1955: 15

Pennesi, Chiara, Majewska, Roksana, Sterrenburg, Frithjof A. S., Totti, Cecilia & Stefano, Mario De, 2018, Taxonomic revision and morphological cladistics analysis of the diatom genus Anorthoneis (Cocconeidaceae), with description of Anorthoneis arthus-bertrandii sp. nov., Phytotaxa 336 (3), pp. 201-238 : 217-219

Anorthoneis hummii Hustedt 1955: 15 ( Figs 49–67 )

References:— Hustedt (1955), p. 15, pl. 2 fig. 6, pl. 5 figs 18–19; Simonsen (1987), p. 405, pl. 605, figs 1–9; Witkowski et al. (2000), p. 97, pl. 42, fig. 22.

Description. Valves outline varies from ovoid to roundish ( Figs 57 , 63 ). Apical axis: 27–41 μm; transapical axis: 23–36 μm.

SV:— Externally, valve face flat to convex, curving abruptly into a shallow, imperforate mantle ( Fig. 58 and 60 ). Sternum depressed, asymmetric, terminating in small roundish hyaline areas, close to the valve margin ( Fig. 57 arrow). Central area not clearly defined ( Fig. 57 ). Transapical striae uniseriate on both the valve face and the mantle, from 8 in 10 μm close to the margin to 10 in 10 μm close to the sternum, composed of large, transapically elongated areolae (10 in 10 μm). Thick hymenes occluding externally the areolae perforated by round porelli in a circular to regular scatter ( Fig. 59 ). Internally, valve face concave, with raised narrow sternum, expanding laterally into large asymmetric roundish central area ( Fig. 62 ). Mantle virgae visibly raised ( Fig. 61 ).

RSV:— Externally, valve face almost flat to slightly concave, sloping gently into a shallow mantle ( Fig. 67 ). Striae radial, uniseriate, becoming biseriate close to the valve margin, 20 in 10 μm ( Figs 65, 66 ). Areolae large, roundish (valve face) or transapically-elongated (mantle), 30 in 10 μm, occluded by hymenes ultrastructurally similar to those in the SV ( Fig. 66 ). Central area very narrow, not well discernible, flanked by imperforated small areolae ( Fig. 64 ). Proximal raphe endings expanded, pore-like, coaxial and lying in concave drop-shaped area ( Fig. 64 ). Distal raphe endings expanded, pore-like, hardly reaching hyaline submarginal areas ( Fig. 65 , arrow), distant from the valve margin. Valvocopula open, with a smooth inner margin ( Figs 65 and 66 ).

Figures

FIGURES 49–56. Historical reports of Anorthoneis hummii by different authors. (49) Raphe-sternum and sternum valve drawings of A. hummii from Hustedt (1955) (holotype); (50) Raphe-sternum valve micrographs of A. hummii from Witkowski et al. (2000); (51, 52) Micrographs of A. hummii specimen H65158 from slide ZT1/87 (Holotype), material AM791 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven,Germany); (53) Micrograph of A. hummii specimen H65433 from slide ZT1/96 (Paralectotype), material AM795 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (54, 55) Micrographs of A. hummii specimen H65252 from slide ZT1/92 (isolectotype), material AM792 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (56) Micrograph of A. hummii specimen H65217a from slide ZT1/90 (lectotype), material AM792 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany). Magnification: Fig. 52: x1500. Scale bars: Figs 51–56 = 10 μm.

FIGURES 57–62. Anorthoneis hummii specimens from Hustedt’s cleaned materials AM791, AM792, Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany), SEM images. (57) External sternum valve with asymmetrical hyaline central area and small roundish terminal areas (arrow); (58) Detail of sternum valve mantle terminating in a wide hyaline marginal area; (59) Detail of roundish/transapically elongated areolae externally occluded by thick perforated hymenes; (60) Detail of sternum valve mantle; (61) Internal view of areolae occluded by perforated hymens; (62) Internal sternum valve showing sternum and hyaline central area. Scale bars: Fig. 57 = 10 μm; Figs 62, 63 = 5 μm; Figs 58, 60 = 2 μm; Figs 59, 61 = 1 μm.

FIGURES 63-67. Anorthoneis hummii specimens from Hustedt’s cleaned materials AM791, AM792, Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany), SEM images. 63. External view of raphe-sternum valve. (64) Detail of coaxial raphe central endings in external view lying in drop-shaped areas; (65) External view of distal raphe ending terminating in hyaline submarginal area; (66) Tilted external view (60°) of raphe-sternum mantle showing the opened valvocopula with smooth inner margin; (67) Tilted external view (60°) of raphe-sternum valve. Scale bars: Fig. 57 = 10 μm, Figs 62, 63, 67 = 5 μm; Figs 58, 60, 65 = 2 μm; Figs 59, 61, 64, 66 = 1 μm.