Parodontella tenuicornis (Greville) D. M. Williams & P.A. Sims, 2018

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 : 13-17

Parodontella tenuicornis (Greville) D. M. Williams & P.A. Sims , comb. nov. ( Figs 51–55 )

Basionym: — Biddulphia tenuicornis Greville (1865b: 51 , pl. 6, fig. 17)

Synonyms: — Odontotropis tenuicornis (Greville) Grunow (1884: 60) Odontotropis tenuicornis (Greville) De Toni (1894: 881) Parodontella obliqua Komura (1999: 64 , figs 16, 17, 107–123)

Type:— “ Barbadoes, Cambridge Estate, Johnson 1862” ( BM 2777 !, holotype of Biddulphia tenuicornis ) ; Nabuto beach, Boso Peninsula, central Japan (MPC-1653, holotype of Parodontella obliqua ) .

Valves broadly lanceolate with apiculate apices, long slender elevation at each pole and four long tubular spines, exterior openings of rimoportulae on valve face ( Figs 51, 53 ). Valve length 42–19μm, breadth 15–53μm, mantle costae 19 in 10μm. Summit of elevation slightly expanded and flattened with 3–4 small marginal linking (?) spines on proximal face, inverted triangular ocellus on distal face ( Fig. 54 ). Well-developed marginal ridge formed by fused mantle costae extending as solid spinules on summit, separates valve face from expanded semi-lanceolate mantle ( Figs 52, 55 ). Areolae loculate, single or bi-seriate rows of poroids forming striae on mantle ( Fig. 55 ), on valve face irregular transapical lines of poroids meeting at central sternum ( Fig. 53 , arrow). Long spines, expanded at base, opening on valve face, occasionally on mantle ( Figs 52, 55 ). Rimoportulae 4, opening on valve face, through long tubular spines, flattened at base, 2 spines positioned sub-marginally at valve centre, 2 positioned either side of sternum towards elevations ( Figs 51, 53 ). No interior view obtained.

Observations:— The description above is based on material from Vema 39573 (9) (‘Vema Cruise 17 South Atlantic, Core Number 107, Water Depth 1525’, BM), Vema 39576/10 (‘Vema Cruise 12, South Atlantic, Core Number 46, Water Depth 1167 m; from top of Core 280; details of the Vema material can be found in Hanna et al. 1976) and Cambridge, Barbadoes (after Greville 1865b). Also found at Calvert County, Pöplein, Maryland, USA.

Figures

FIGURES 51–55. Parodontella tenuicornis (Greville) D.M. Williams & P. A. Sims (Vema Cruise 17, core 107,120 cm). Fig. 51. Valve exterior tilted with long narrow elevations at apices, valve face bordered by marginal ridge of fused spines and four stout hollow spines (which are the openings from rimoportulae) extending beyond the height of the elevations; scale bar = 30 μm. Fig. 52. Detail of hyaline elevation with spathulate summit, valve face covered in long spinules; scale bar = 15 μm. Fig. 53. Exterior flat, valve face extending almost to apices, annulus (sternum) (arrow) extending midway between elevations with transapical rows of poroids above locular walls; scale bar = 38 μm. Fig. 54. Flattened summit of elevation with margin of small triangular spines, on distal face a triangular ocellus, its base towards summit; scale bar = 2 μm. Fig. 55. Valve mantle with biseriate rows of poroids between barely raised vertical costae; scale bar = 5 μm.