From Fensome et al., 2019:
Impletosphaeridium capillaceum Morgenroth, 1966a, p.33, pl.9, fig.12. Holotype: Morgenroth, 1966a, pl.9, fig.12. Age: Early Eocene.

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Original description: [Morgenroth, 1966a]:

Impletosphaeridium capillaceum n. sp.
Plate 9 Fig. 12

Derivatio nominis: capillaceus Latin: hairy (cf. extensions).
Holotype: The specimen preserved in specimen HF No. 68 and illustrated in Plate 9 Fig. 12.
Paratypoids: In specimen HF No. 2, HF No. 10, HF No. 73.
Locus typicus: Fehmarn, Katharinenhof.
Stratum typicum: Lower Eocene (?2).
Diagnosis: The small, thin-walled, delicate capsule has an elliptical outline and is evenly covered with the finest, relatively rigid, massive, simple hairs, almost resembling fur. - Pylomata were not observed.
Comparison: The new species is very similar to Impletosphaeridium whitei (DEFLANDRE & COURTEVILLE), but differs from it in its smaller dimensions.
Dimensions: Capsule length 24μ (22μ/25μ), capsule width 22μ (20μ/25μ), process length: 4μ-6μ (7 measurements).
Number of specimens examined: 7