From Fensome et al., 2019:
Trithyrodinium robustum Benson, 1976, p.199,200,202, pl.11, figs.9–12; pl.12, fig.1.
Holotype: Benson, 1976, pl.11, figs.9–12; pl.12, fig.1.
NOW Chatangiella?. Originally Trithyrodinium, subsequently (and now) Chatangiella?.
Taxonomic junior synonym: Trithyrodinium inequale (name not validly published), according to Slimani (2001a, p.192).

Locus typicus: Round Bay, Maryland
Stratum typicum: Late Maastrichtian

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Original diagnosis: Benson, 1976, p.198
Cavate cyst with pronounced apical horn, antapical horns, and large circular to elliptical endoblast. Left antapical horn twice as long as right. Tabulation reflected by intratabular coni: 4", 3a, 6-7", ?c, 5""", 1p, 2"""". Archeopyle type 3I on endoblast, type I on periblast. Cingulum levorotary, slightly greater than 1 cingulum width. Sulcus restricted to hypotract, up to 15 Ám in width. Endoblast microreticulate to microgranulate. Endophragm 1Ám in thickness, increasing to 2 Ám at apical and antapical ends. Periphragm slightly less than 1 Ám in thickness.
Dimensions: Holotype: Periblast length 153 Ám; width 78 Ám; endoblast length 69 Ám; width 71 Ám; apical pericoel 43 Ám.