Entogoniopsis, Witkowski & Sims & Strelnikova & Williams, 2015

Witkowski, Jakub, Sims, Patricia A., Strelnikova, Nina I. & Williams, David M., 2015, Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser, Phytotaxa 209 (1), pp. 448-450 : 448-450

16. Entogoniopsis ? sp. 1 (SEM: Figs 205–211 )

Frustule subrectangular in girdle view ( Fig. 209 ), valve outline tripolar ( Figs 205, 207 ), with acute poles and straight sides. Valve face undulate, with a distinct trifolium bearing a small hyaline area at the centre ( Fig. 205 ), within which there may or may not be rimoportulae ( Figs 205, 207 ). Low elevation that bears a prominent, hooked linking spine at its distal face is present at each pole ( Figs 205, 210–211 ). A hyaline marginal ridge extends between each polar elevation ( Fig. 205 ). In the two sibling valves the hyaline marginal ridge is level with the summits of the polar elevations ( Fig. 209 ), and there are additional small interlocking linking devices in even intervals along the crest of the ridge ( Figs 209–210 ). The valve that lacks a sibling has a lower marginal ridge that appears to follow the valve face undulations, and without the linking devices

28 • Phytotaxa 209 (1) © 2015 Magnolia Press

WITKOWSKI ET AL.

( Fig. 205 ). Radially oriented, locally curved hyaline costae are present on the valve face exterior ( Fig. 205 ). Whole valve face is perforated by poroid areolae with radial, slightly domed cribra ( Fig. 211 ). Mantle is shallow, steeply downturned, perforated by rows of poroid areolae parallel to the pervalvar axis ( Fig. 207 ), slightly divergent closer to the poles. Margin of the mantle is hyaline, smooth, and slightly expanded inwardly ( Fig. 207 ). Along each side on the valve interior, there is a series of robust costae that arise from the expanded mantle margin and project a short distance toward the valve face centre ( Fig. 207 ). At least two copulae were observed. Valvocopula is closed, relatively deep, with only two poorly defined rows of poroid areolae near the advalvar margin ( Figs 205, 209 ). Copula is closed, shallower than the valvocopula, mostly hyaline, with only a single row of poroids near the advalvar edge ( Figs 205, 209 ). Remnants of a third girdle element can be seen projecting from underneath the copula, but are not interpretable ( Fig. 211 ).

Geographic and stratigraphic distribution ( Fig. 10, site 23):

Middle Miocene : Szurdokpüspöki (‘Castel’), Hungary: BM stub P.1352 ( Figs 205–211 ).

Observations:— Despite considerable effort, only a single specimen was found and that could only be examined in SEM. The presence of linking spines and secondary interlocking linking devices located along the crest of the hyaline marginal ridge, heterovalvy with respect to the presence or absence of rimoportulae, the absence of pseudocelli, and the lack of compelling evidence for valvocopula attachment to the internal costae suggest that this taxon might represent a separate genus. However, given the insufficient data, and the lack of further specimens with which to typify it, we are reluctant to describe this as new species and provisionally identify it as an unknown species of Entogoniopsis .

New combinations

Figures

FIGURES 205–211. Scanning electron micrographs of Entogoniopsis? sp. from Szurdokpüspöki (‘Castel’), Hungary. Fig. 205: Oblique external view of a short chain. Note the prominent, curved linking spine preserved on the lower pole (arrow), and the lack of external openings of the rimoportulae within the central area. VC: valvocopula, C: copula. Fig. 206: Internal view of the central area, showing the internal openings of the rimoportulae. Fig. 207: Oblique internal view of the sibling valve, showing the location of the rimoportulae within the central area (arrowhead), and a series of prominent internal costae along the valve margin (arrow). Fig. 208: Detail of the poles, tightly linked by hooked linking spines. Fig. 209: Girdle view of a short chain showing additional interlocking linking devices along the crest of the marginal ridge (arrows). Note that the valve to the right of the micrograph differs in structure of the marginal ridge. Arrowhead indicates polar linking spines. Fig. 210: Detail of the sibling valves, showing the interlocking linking devices along the crest of the marginal ridge. Fig. 211: Detail of a polar elevation, showing a cross-section through a fractured spine (arrowhead).