Amphitetras antediluviana Ehrenberg (1839

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 : 27

Amphitetras antediluviana Ehrenberg (1839 [ 1841]: 142; 1840b: 62) ( Figs 95–100 )

Synonyms:— Triceratium antediluvianum (Ehrenberg) Grunow (1867: 24) Biddulphia antediluviana (Ehrenberg) Van Heurck (1885: 207) Odontella antediluviana (Ehrenberg) M. Peragallo (1903: 686)

Type:— “Fossil in den Kreidemergeln von Oran und Griechenland, lebend bei der Insel Tjörn am Cattegat” ( Ehrenberg 1839 [ 1841]: 142; 1840b: 62)

Valves quadrangular with rounded apices and concave margins ( Fig. 95 ), length between poles 35–115μm. Apices barely raised into elevations, each with a large circular ocellus mostly on distal face slanting outwards ( Figs 97, 98 ). Valve face with central circular dome with depressed centre ( Fig. 95 ), valve face merging into a rounded mantle linked by buttressed costae at its base to a broad, flat hyaline valve margin with raised border ( Fig. 97 ). Network of anastomosing costae cover valve face, mantle and elevations, each enclosing a single large poroid areola ( Fig 96 ). Two types of vela occlude poroid areolae, mostly an elaborate cribrum with occasional attachment points, rarely a specialised pore with scalloped margin ( Fig. 96 , arrow). No rimoportulae visible. Girdle bands visible, valvocopula closed with inwardly directed pars interior, all bands with poroid areolae occluded by cribra ( Fig. 96 ).

Observations:— Further details on Amphitetras antediluviana can be found in Mayama and Fujita (1995) and Round et al. (1990).

The description above is based on material from Port Shepstone, Natal, South Africa.

Figures

FIGURES 95–100. Amphitetras antediluviana Ehrenberg (Port Shepstone, Natal, South Africa). Fig. 95. Quadrangular valve exterior with broadly rounded apices and attached valvocopula; valve surface covered in anastomosing costae, valve centre depressed; scale bar = 10 μm. Fig. 96.Anastomosing costae with surface spinules enclosing poroid areolae mostly occluded by cribra with occasional specialised pores (arrow); scale bar = 2 μm. Fig. 97. Mantle view of valve with barely raised elevations and attached girdle bands; scale bar = 10 μm. Fig. 98. Detail large rimmed ocellus, distally inclined, cribra and specialised pore; scale bar = 2 μm. Figs 99–100. Reproduction of Ehrenberg’s original drawing of Amphitetras antediluviana (Ec 100, housed in Berlin: http://download.naturkundemuseum-berlin. de/Ehrenberg/Ec%20Drawings/Ec%20draw%20001-999/Ec%20draw%20100-199/Ec%20dr%200100.jpg), the published illustration appearing in Ehrenberg (1854: pl. 19, fig. 19).