Trilamina P.A. Sims, J. Witkowski, N.I. Strelnikova & D.M. 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

II. Trilamina P.A. Sims, J. Witkowski, N.I. Strelnikova & D.M. Williams , gen. nov.

TYPE:— Trilamina nitescens (Greville) J. Witkowski, P.A. Sims, Strelnikova & D.M. Williams , comb. nov.

[= Triceratium nitescens Greville (1865a: 8 , pl. II, fig. 19)].

Frustules rectangular in girdle view, valves tri-to quadripolar, with deeply concave sides and tapering or broadly lobed projections distinctly cut off from the mostly hyaline valve centre. Rimoportulae, if present, indistinct and located offcentre within the central area. Central part of each projection depressed, either hyaline or perforated by poroid areolae. Marginal part of the valve raised, and perforated by poroid areolae arranged in short rows parallel to pervalvar axis. Indistinct pseudocelli located at the poles. Valve face-mantle junction gradual, mantle steep, shallow. Internal costae present along the sides of projections, sometimes also associated with the depressed areas within projections; additional internal costae occur in some species on the underside of the central area-Valvocopulae are closed, comparable in depth to the mantle, mostly hyaline, with few rows of poroids next to the advalvar edge. The valvocopula attachment mechanism consists of (1) small clasping devices that attach to the internal costae; (2) fossa that attaches to the inward expansion of the hyaline mantle margin; and (3) large clasping devices that attach to the internal folds associated with the margins of the central area (a synapomorphy for this genus).

Stratigraphic range: middle Eocene-middle Miocene

Habitat: Neritic, likely benthic.