Encyonema jordanii (Grunow ex Cleve 1894: 169 ) F.W. Mills (1934: 639)

Harper, Margaret A., Vijver, Bart Van De, Kaulfuss, Uwe & Lee, Daphne E., 2019, Resolving the confusion between two fossil freshwater diatoms from Otago, New Zealand: Encyonema jordanii and Encyonema jordaniforme (Cymbellaceae, Bacillariophyta), Phytotaxa 394 (4), pp. 231-243 : 239

Encyonema jordanii (Grunow ex Cleve 1894: 169) F.W. Mills (1934: 639) ( Figs. 25–65 )

Basionym: — Cymbella jordani Grunow ex Cleve (1894) Kongliga Svenska-Vetenskaps Akademiens Handlingar 26(2): 169; pl. 5, fig. 3–4

Original description: —“40. C. ( Encyonema ) Jordanii Grun. Ms.—Valve with very elevated dorsal margin, more or less gibbous ventral margin and truncate to capitate ends. Length 0,02 to 0,032; Breadth 0,008 to 0,009 mm. Areas indistinct. Median line straight, terminal fissures turned downwards. Striae about 16 in 0,01 mm radiate in middle, very finely punctate.”

Isotype: — New Zealand, Otago, sample T1/71 HB, held in the collections of Botanic Garden Meise, Belgium (BR).

Type Locality: —Fresh Water: Otago, New Zealand (Weissflog Collection).

Age:—Uncertain. Probably fossil.

Light microscopy ( Figs 25–61 ): —Valves clearly dorsiventral and curved along the apical axis, with a strongly convex dorsal and moderately tumid ventral side. Apices protracted, capitate to subcapitate, ventrally bent. Smaller specimens with broadly rounded, non-protracted apices ( Fig. 60 ). Valve dimensions (n=50): length 13–40 μm, width 7–9.5 μm. Axial area narrow, linear, slightly widening towards the central area. Central area totally absent to very small, rounded to elliptical. Raphe branches straight to weakly bent, filiform with weakly deflected, simple proximal raphe endings and ventrally bent, long terminal fissures. Dorsal striae curved, radiate near the valve center, becoming parallel towards the apices, 17–23 in 10 μm. Central striae more widely spaced than the others. Ventral striae parallel in the middle, slightly radiate to parallel in the rest of the valve, 18–20 in 10 μm. Areolae usually discernible in LM, <30 in 10 μm.

Scanning electron microscopy ( Figs 62–65 ): —Striae uniseriate, composed of rounded to squarish, relatively large areolae ( Fig. 62 ). External raphe branches ventrally curved ( Fig. 62 ). External proximal raphe endings indistinct, straight. Terminal raphe fissures usually elongated, ventrally bent. Some valves observed with short, straight terminal fissures ( Fig. 63 ). Internally, distal raphe endings terminating onto small helictoglossae. Proximal internal raphe endings clearly dorsally bent, presenting short hooks ( Figs 64, 65 ).

Figures

FIGURES 25–61. E. jordanii. 25–43. Light micrographs from sample AT82 (Encyonema jordani, Otago, New Zealand, Weissflog Collection, Jordan, 4/1882) present in the Hustedt Collection in Bremerhaven (Germany). 44–61. Light micrographs from sample Slide VIII-2-B1 (Van Heurck Collection, Botanic Garden Meise, Belgium). Scale bar represents 10 μm.

FIGURES 62–65. Scanning electron micrographs from sample AT82 (Encyonema jordani, Otago, New Zealand, Weissflog Collection, Jordan, 4/1882) present in the Hustedt Collection in Bremerhaven (Germany). 62. External view of an entire valve. 63. External view of the valve apex showing the terminal raphe fissure. 64. Internal view of an entire valve showing the helictoglossa and the deflected proximal raphe endings. 65. Internal view of the central area showing the intermissio and the square-shaped areolae. Scale bar represent 10 μm in figs 62, 64 and 1 μm for figs 63, 65.