Oligosphaeridium umbraculum Duxbury, 2001, p.109–111, fig.10, nos.1–4.
Holotype: Duxbury, 2001, fig.10, nos.1–2.
Age: early Hauterivian.

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Original description (Duxbury, 2001):

Oligosphaeridium umbraculum n. sp.

Holotype: Figures 10.1 and 10.2.
Type Locality: Well 13/24-1 at 5490 ft (ditch cutings), Early Hauterivian, E.F. H24.2.
Derivation of Name: From the Latin umbraculum, a parasol, referring to the very broad process terminations of this species.

Diagnosis: A very large, thin-walled, chorate dinocyst species. The smooth, spheroidal central body bears 19 paraplate-centred, tubular processes, which expand distally into very large, distinctive terminations which may approximate half the main body diameter. Process terminations are polygonal in plan view, often pentagonal, and possibly mimicking plate outlines; some denticles may occur along the margins of these terminations. Large but rare holes are often present within the process terminations, and rare trabeculae may be present between them. The archeopyle is apical, tetratabular, and the operculum is invariably detached.

Dimensions: Holotype: 132 x 129 μm
Overall: 168 (151) 132 × 142 (133) 129 μm
Specimens Measured - 4

Comments: The process terminations are reminiscent of Oligosphaeridium perforatum (GoCHT, 1959) DAVEY & WILLIAMS, 1969 and the occa-
sional occurrence of trabeculae is reminiscent of Oligosphaeridium junctum BAILEY & LOY, 1997. However, in its overall structure, Oligosphaeridium umbraculum n. sp. is a very distinctive species.