Pseudictyota reticulata (Roper) P.A. Sims & D. M. Williams, 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 : 32-35

Pseudictyota reticulata (Roper) P.A. Sims & D. M. Williams , comb. nov. ( Figs 117–121 )

Basionym:— Biddulphia reticulata Roper (1859: 14 , pl.2, figs 13–15)

Synonyms:— Triceratium dictyotum P.A. Sims & R. Ross (1990: 168 ≡ Biddulphia reticulata Roper ) Odontella? reticulata (Roper) De Toni (1894: 868) rr

Type:—“ Trincomalee and Natal, Roper; New Zealand, Dr. Arnott-Walker ” ( Roper 1859: 14); SRI LANKA:—Trincomalee ( BM 21234 , BM 22780 , BM 22787 , syntypes) ; SOUTH AFRICA: Natal ( BM 22788 , syntypes) ; NEW ZEALAND ( BM 21711 , BM 22608 , BM 22786 , BM 22782 , syntypes) .

Valves bipolar, length 70–132μm, breadth 35–82μm. Valve outline broadly lanceolate with a barely raised elevation at each pole ( Figs 118–119 ). Elevation with circular, rimmed ocellus at summit ( Fig. 119 ). Valve face slightly convex with steeply sloping rounded mantle, valve margin expanded with raised border ( Fig. 117 ). Valve exterior covered in false pseudoloculi, irregular in outline, spinule above each junction, mostly 2 false pseudoloculi in 10μm. Basal surface punctured by uninterrupted rows of poroid areolae, up to 12 in each false pseudoloculus. Poroid areolae occluded by two types of vela, mostly by raised cribra, occasional specialised pore, usually larger in size, with one in each pseudoloculus ( Fig. 121 , arrow). Valve mantle attached to edge of valve margin by buttressed costae with splayed ends. Single rimoportula (occasionally 2) located at proximal base of each elevation, its external opening through short, narrow buttressed spine ( Fig. 119 ), internally a slit between raised lips.

Observations:— Further images can be found in Ross and Sims (1971: pl. 4, figs 5, 6) and Diatom 18 (2002: cover image of frustule, photo by T. Nagumo).

This description is based on specimens from Thursday Island, Queensland, Australia; Hog Harbour, New Hebrides [Espiritu Santo, Vanuatu]; Ambrim, New Hebrides [Ambrym, Vanuatu]; Philippines.

Figures

FIGURES 117–121. Pseudictyota reticulata (Roper), P.A.Sims & D.M. Williams. nov. sp. Fig. 117. Reproduction of plate 2, figs 13–15 for Biddulphia reticulata from Roper (1859) (not to scale). Fig. 118. Thursday Island, Queensland. Bipolar valve with elevations at apices and irregular network of false pseudoloculi covering valve face and mantle; scale bar = 10 μm. Fig.119.Ambrin, New Hebrides [Ambrym, Vanuatu]. Ocellus at summit of elevation, note expanded hyaline valve margin with raised border and openings from two rimoportulae; scale bar = 1 μm. Fig. 120. Philippines. Mantle view with attached girdle bands; valve covered with ridged spinules; scale bar = 25 μm. Fig. 121. Hog Harbour, New Hebrides [Espiritu Santo, Vanuatu]. False pseudoloculi; basal layer of poroid areolae mostly occluded by raised cribra with a specialised pore (arrow) in most sectors; scale bar = 2 μm.