Cribrionella ohridana Jovanovska, Cvetkoska, Tofilovska, Ognjanova-Rumenova & Levkov, 2016

Jovanovska, Elena, Cvetkoska, Aleksandra, Tofilovska, Slavica, Ognjanova-Rumenova, Nadja & Levkov, Zlatko, 2016, Description of a new fossil diatom genus, Cribrionella gen. nov. (Bacillariophyta) from Quaternary sediments of Lake Ohrid, Phytotaxa 252 (1), pp. 31-42 : 34

Cribrionella ohridana Jovanovska, Cvetkoska, Tofilovska, Ognjanova-Rumenova & Levkov , sp. nov. ( Figs 2–61 )

Valves circular in shape, 2.0–7.5 μm in diameter ( Figs 2–61 ). Central area flat, variable in size and shape: large circular to small circular-elongate, or absent. From valve exterior, some specimens with ornamented central area, bearing irregularly shaped depressions that do not penetrate valve wall interior ( Figs 50, 54 ). Internally, valve central part covered with central lamina, variable in size and shape ( Figs 55, 56 ). Valve marginal lamina with submarginal alveoli interrupted with thick and inwardly raised circumferential silica trabeculae (black arrow in Fig. 56 ). The submarginal alveoli followed by 2–4 regularly or irregularly arranged areolae. Striae coarse composed of large and round areolae ( Figs 7, 23, 31 , 49, 50, 52 ). From outside, submarginal alveoli and areolae occluded by cribra ( Figs 49, 51, 52 ), surrounded by small cribrate openings slightly depressed into valve surface (white arrow in Fig. 53 ). From inside, areolae separated with thick silicified bars (black arrow in Fig. 57 ). Internally, each areola crossed by 1 – 2 thick and inwardly raised circumferential silica trabeculae (black arrow in Fig. 58 ). Single marginal rimoportula present; externally situated on costa, with relatively wide and round opening (arrow in Fig. 49 ). Internally, rimoportula with sessile labium positioned on costa, very close to alveolar opening, in oblique direction (black arrow in Fig. 60 ). Marginal fultuportulae on every 4 – 5 costa, with round and simple external opening, positioned on valve-mantle junction ( Figs 50 – 52 , black arrow in Fig. 53 ). Internally, each marginal fultoportula with short central tube, laterally surrounded by two satellite pores ( Figs 60, 61 ). Valve face fultoportulae absent. From outside, ring of small granules present at valve-mantle junction ( Figs 49, 50, 53 ). Valvocopula closed, bearing 1 – 3 rows of pores (black arrows in Figs 51 , 59 ).

Type:— MACEDONIA. Lake Ohrid: site DEEP, core 5045-1, 41° 02’ 57” N, 20° 42’ 54” E, sediment samples from a 185.39 m depth composite core, March–June 2013 (holotype: MKDNC!, circled specimen on slide 009499, specimen illustrated on Fig. 13 . Isotype: BRM! ZU10/65).

Etymology:— The specific epithet “ ohridana ” resembles the type locality Lake Ohrid where the species is described from.

Distribution:— Freshwater fossil species observed only from its type locality, the core samples from Lake Ohrid.

Figures

FIGURES 2–48: Cribrionella ohridana gen. & sp. nov., LM valve views. 13. Holotype specimen. Scale bar = 10 μm.

FIGURES 49–54: Cribrionella ohridana gen. & sp. nov., SEM external valve views. 49. Valve view, showing the external opening of the rimoportulae (see black arrow). 50. View of the whole frustule, note the ring of granules present on the valve-mantle junction, and the marginal fultoportulae. 51. Broken valve, note the pores on the valvocopula (black arrow). 52. View of a broken frustule. 53. Detailed view of the cribrate occlusions; the small granules; and the marginal openings of the fultoportulae (see black arrow). 54. Close view of the valve central area, note the irregularly shaped depressions. Scale bars = 2 μm (Figs 50, 52), 1 μm (Figs 49, 51, 54), 0.5 μm (Fig. 53).

FIGURES 55–61: Cribrionella ohridana gen. & sp. nov., SEM internal valve views. 55. Valve view. 56. Broken valve showing the submarginal alveolus (see black arrow). 57. Close view of areolar openings, separated from each other by a thick silica bars (see black arrow). 58. Detailed view of the areolar openings interrupted by thin and inwardly raised circumferential silica trabeculae, dividing the cribrum into two-three separate parts (see black arrow). 59. Note the pores on the valvocopula (back arrow). 60. Close view of the marginal fultoportulae (see white arrow) and the rimoportulae (see black arrow). 61. Marginal fultoportulae surrounded by two satellite pores, cowlings absent. Scale bars = 2 μm (Fig. 55), 1 μm (Figs 56, 60), 0.5 μm (Figs 57–59), 0.2 μm (Fig. 61).