Ataxiodinium elongatum, Zevenboom and Santarelli in Zevenboom, 1995, p. 141-142, pl.1, figs.7-12.

Name not validly published: considered a manuscript name by the authors.
Taxonomic senior synonym: Ataxiodinium zevenboomii, according to Head (1997, p.171-172).

Holotype: Zevenboom, 1995, pl.1, figs.7-9.
Type locality: Heumensoord Well, The Netherlands.
Type stratum: Haps Formation.
Occurrence: The Netherlands (this study), Australia (McMinn, 1992).
Total stratigraphical range: ? Upper Miocene to Early Pliocene (this study).
Age: ?Late Miocene-Early Pliocene.

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Original description: [Zevenboom, 1995]:

Diagnosis:
A species of Ataxiodinium characterized by an elongate shape. The periphragm consists of numerous small funnel shaped extensions. The endophragm is smooth while the periphragm is faintly granular.

Description:
A species of Ataxiodinium characterized by a distinctly elongate shape. The periphragm consists of numerous small small funnel shaped extensions 2 to 5 µm in size. The endophragm is thin and smooth. The periphragm is faintly granulate.
No tabulation is indicated except by the archaeopyle. The archaeopyle is precingular and most probably formed by the loss of paraplate 3". The operculum is free.

Dimensions:
Height: 38(42)43 µm; width: 31 (33) 34 µm; Wall thickness: 0.5 µm: Height of periphragm: 2 (3.5)5. N=10

Discussion:
Ataxiodinium elongatum differs from A. choanum Reid, 1974 and A. confusum Versteegh and Zevenboom, 1995, the other described species in the genus by its elongate shape and by having more and smaller funnel shaped extensions or 'bubbles'.