From Fensome et al., 2019:
Callaiosphaeridium asymmetricum ssp. latum Heilmann-Clausen in Heilmann-Clausen and Thomsen, 1995, p.290–291, pl.14, figs.3–4;
text-fig.13. Holotype: Heilmann-Clausen and Thomsen, 1995, pl.14, fig.3; text-fig.13. Age: early Barremian.

---------------------------------------------------------------------------------------------------

Original description: [Heilmann-Clausen and Thomsen, 1995, p. 290-291]:

Diagnosis:
This is a subspecies of Callaiosphaeridium asymmetricum in which the proximal part of the paracingular processes are laterally much expanded, so as to coalesce with the neighbouring paracingular processes. A septum-like, hollow structure thus occupies the entire paracingulum.

Dimensions:
of holotype: Central body breadth 37 µm, dorso-ventral diameter 38 µm. Pericyst breadth 77 µm, dorso-ventral diameter 78 µm.
of measured specimens: Central body breadth: 35 (40) 44 µm. Central body dorso-ventral diameter: 34 (38) 42 µm. Pericyst breadth: 73 (84) 98 µm. Pericyst dorso-ventral diameter: 66 (80) 95 µm. (8 specimens measured)