Leptodinium churchillii Harland, 1968, p.548,550–551, figs.12–13,22–24.

Originally Leptodinium, subsequently Impagidinium.
Taxonomic senior synonym: Hystrichosphaera (now Spiniferites) nodosa, according to Reid (1974, p.599).
Taxonomic senior synonym: Hystrichosphaera (now Spiniferites) bentorii according to Harland (1977b, p.98–99) — however, Leptodinium churchillii is now generally considered a taxonomic junior synonym of Hystrichosphaera (now Spiniferites) nodosa.

Holotype: Harland, 1968, figs.12-13, 22-24
Locus typicus: Borth Bog, Cardiganshire, Wales
Stratum typicum: Holocene

Original diagnosis: Harland, 1968, p.548
Ovoidal to ellipsoidal test, having the endophragm and periphragm in close juxtaposition except at the apex where a pericoel is developed. The tabulation is 4", 6"", 6c, 5""", 1p, 1p.v., 1"""" . The cingulum is helicoid. The sulcus extends onto the epitract and hypotract and is undividcd. The plates are divided by low crests bearing occasional gonal processes. These are small, cylindrical and slender. The archaeopyle is precingular formed by the loss of plate 3"".
Dimensions: The central body measures 60 µm from apex to antapex and the width measures 45 µm.