From Williams et al., 2017:

[Pyramidium, Clarke and Verdier, 1967, p. 39-40

Name illegitimate
Tax. sr. syn.: Oodnadattia, according to Below (1981a, p.64) - however, Lentin and Williams (1981, p.238,294) retained Xiphophoridium.

Type species: originally as Hystrichodinium alatum, Cookson and Eisenack, 1962b (pl.2, fig.1)] ; Pyramidium alatum, Clarke and Verdier, 1967

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Original description: [Clarke and Verdier, 1967]:

Diagnosis:
Overall shape pyramidal. Tabulation present. Girdle present and displaced ventrally. Plates bordered by ledges bearing processes of which those at the junction of the septa are the longest. Wall smooth or ornamented with tubercles or verrucae.
Archaeopyle apical.