From Fensome et al., 2019:
Cerodinium Autonym. Holotype: Alberti, 1959b, pl.9, fig.18. Originally Deflandrea diebelii subsp.
diebelii, subsequently Ceratiopsis diebelii subsp. diebelii (combination illegitimate), thirdly (and now)
Cerodinium diebelii subsp. diebelii.

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Original description as Deflandrea diebelii: [Alberti 1959, p. 99-101]: (Translation: LPP):

Description:
Shell flattened, elongate. Epitheca mostly a sharp-cornered triangle, distally narrowing into along horn. Transversal furrow mostly absent and if present slightly deepened. Two long antapical horns which, like the apical horn, sometimes bear a fine longitudinal striation. Inner body oval, positioned close to the shell.
Additions: The species is characterized by the long horns, which narrow distally and which are pointed or slightly blunt. The horns are almost equal in length. The membrane of the armor is soft, transparent and sometimes finely punctate. A rounded trapezium-shaped archaeopyle is located closely below the apex.

Dimensions:
Length central body: 110-210 µm; width central body: 40-50 µm.

Affinities:
Deflandrea diebelii differs from all other species in this genus in the outline of the shell and the very large horns.