Amphipentas boryana (Pantocsek) De Toni (1894: 912)

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 : 23

Amphipentas boryana (Pantocsek) De Toni (1894: 912) ( Figs 81–86 )

Basionym:— Triceratium boryanus [= “ Triceratium (Grovei Pant. var?) boryanum n.s.”] Pantocsek (1889: 88; 1892: pl. 33, fig. 476 = “ Triceratium boryanum Pant. ”)

Type:— “Bory” ( Pantocsek 1889: 88)

Valve outline pentagonal ( Figs 81–83 ), 140–160μm diagonally from pole to pole, with barely raised triangular elevations at each pole, ocellus at each summit. Valve face with central circular dome with depressed valve centre ( Fig 82 ). Valve mantle shallow, lying vertically to valve face and linked by costae to inner end of extended flat valve margin with raised border ( Fig. 84 ). Linked anastomosing costae cover valve face, elevations and mantle forming quadrangularhexagonal sectors ( Fig. 82 ), a granule above each junction ( Figs 84, 86 ). On domed area, costae distinctly radially aligned with less obvious interstices ( Fig. 82 ). Within each sector lies a single large poroid areola occluded by two types of vela, mostly by elaborate raised cribra, occasionally by specialised pores with volae extending from margin ( Fig. 86 ). Rimoportulae 5, each positioned midway between two elevations on radially aligned costa, external openings through small, short tube, internally through slit across a papillus ( Fig. 85 ).

Observations:— A quadrangular form, which may be the same species, is known as Tricertium grovei Pant. (“ Tricertium (acutangulum Grev. var.?) grovei nov. spec.” in Pantocsek 1886: 52). It is smaller and differs with the valve face being barely raised.

The description above is based on material from Szurdokpüspöki, Hungary, and Bory, Slovakia, Miocene.

Figures

FIGURES 81–86. Amphipentas boryana (Pantocsek) De Toni (Castel, Szurdokpüspöki, Hungary). Fig. 81. Reproduction of illustrations for Triceratium boryanum from Pantocsek (1892: pl. 33,fig. 476) (not to scale). Fig. 82. Exterior pentagonal valve with elevations at each angle, a depressed valve centre and regular network of anastomosing costae covering valve face and mantle; scale bar = 10 μm. Fig. 83. Valve interior with attached girdle band, note openings from rimoportulae positioned at base of valve centre midway between elevations; scale bar = 60 μm. Fig. 84. Ocellus with hyaline rim, mantle merging into expanded hyaline valve margin with raised border; scale bar = 6 μm. Fig. 85. Valve interior with radial rows of poroid areolae and openings from rimoportulae, a slit across a papillus; scale bar = 10 μm. Fig. 86. Anastomosing costae enclosing a single poroid areola, most occluded by cribra with an occasional specialised pore (arrow); scale bar = 4.3 μm.