From Fensome et al., 2019:
Trabeculodinium quinquetrum Duxbury, 1980, p.133–134, pl.9, figs.1–2,5.
Holotype: Duxbury, 1980, pl.9, fig.2; Fensome et al., 1995, fig.2 — p.1729.
Originally (and now) Trabeculidium, subsequently Nematosphaeropsis. Lentin and Williams (1993, p.649) retained this species in Trabeculidium.

Locus typicus: Speeton Clay, Speeton, England
Stratum typicum: Barremian

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Original diagnosis: Duxbury, 1980, p.132
A species of dinoflagellate cyst whose main body is pentagonal in lateral view due to its having a distinctly triangular epicyst and sharp-angled, trapeziform hypocyst. Trifurcate gonal and bifurcate parasutural processes are present and these vary in length so that despite the polyhedral shape of the main body, the cyst as a whole is spheroidal. Both gonal and parasutural processes are proximally unconnected and distally joined by solid, thin trabeculae. Each parasutural line is distally reflected by two trabeculae. The archeopyle is precingular, formed by detachment of paraplate 3".
Observed Dimensions: Holotype--76 x 76 µm. Overall--81 (74) 68 x 78 (70) 59 µm.