Zygoceros ehrenbergii Sar

Sims, Pat A., Williams, David M. & Ashworth, Matt, 2018, Examination of type specimens for the genera Odontella and Zygoceros (Bacillariophyceae) with evidence for the new family Odontellaceae and a description of three new genera, Phytotaxa 382 (1), pp. 1-56 : 20

Zygoceros ehrenbergii Sar (in Lavigne et al. 2016: 328) ( Figs 72–75 )

Synonyms:— Denticella rhombus Ehrenberg (1844b: 79) Odontella rhombus (Ehrenberg) Kütz. (1849:136)

Type:— Petersburg, Virginia, 231208-e BHUPM = Sar et al. 2007: fig. 4, reproduced here as Fig. 73 , lectotype.

Valve outline broadly lanceolate, valve face convex with elevation at apices ( Fig. 72 ), length 48–105um, breadth 25–55μm, mantle depth up to 18μm. Elevations 7–12μm high (measured from valve face), slanting outwards but not beyond extended valve margin, ocellus on summit. Valve structure loculate, valve surface covered in solid spines ( Figs 73–75 ). Loculi arranged in rows radiating from narrowly lanceolate annulus ( Fig. 75 ), rarely an apical central line ( Fig. 74 ), with 8 areolae in each row and 10 rows in 10μm. Valve centre mostly with annulus, often within hyaline border, areolae within mostly irregular and apically aligned. Rimoportulae mostly 4–6, rarely 3 or 7, positioned submarginally opening through thick, long, hollow spines (see Andrews 1980: 25, pl. 1, figs 6, 7; pl. 4, figs 2, 3).

Observations:— The above description is based on material from Petersburg, Virginia, fossil ( BM Adams A. 486).

Figures

FIGURES 72–75. Zygoceros ehrenbergii Sar (St. Petersburg, Virginia, USA). Fig. 72. Reproduction of Ehrenberg’s original drawing of Denticella rhombus, the published illustration appearing in Ehrenberg (1839: pl. 4, fig. 11). Fig. 73. LM of holotype specimen (from Sar et al. 2007: fig. 4). Figs 74–75. BM Adams A. 486, strewn slide from St. Petersburg, type locality of Denticella rhombus. Fig. 74. Valve with very narrow apical annulus (sternum) at valve centre, valve length 107 μm, breadth 55 μm. Fig. 75. Valve with well-defined annulus (sternum) at valve centre; length 95 μm, breadth 48 μm.