From Fensome et al., 2019:
Amphorosphaeridium fenestratum var. dividum, Davey, 1969c, p.32–33, pl.2, figs.5–6; text-fig.2.
Holotype: Davey, 1969c, pl.2, fig.5; Fensome et al., 1993a, fig.1 — p.1135; fig.2 — p.1181.
NOW Amphorosphaeridium fenestratum subsp. dividum.
Originally Amphorosphaeridium fenestratum var. dividum, subsequently (and now) Amphorosphaeridium fenestratum subsp. dividum.
Age: Campanian–Maastrichtian.

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Original description as Amphorosphaeridium fenestratum var. dividum: [Davey, 1969, p. 32-33]:

Diagnosis:
A variety of A. [Amphorosphaeridium] fenestratum Davey possessing strongly developed processes which are sometimes branched.

Description:
The proportion of branched to unbranched processes varies considerably - from two to three to over half the processes may be affected. Normally the process bifurcates simply, either proximally or medially, but occasionally each branch in turn subdivides once or twice more. Thus one process may give rise to as many as six branches, all of which terminate at a more or less constant distance from the central body. The finer processes appear to be solid and terminate more simply than the tubiform processes. There are one to two processes per plate area.

Dimensions:
Holotype central body diameter 56 x 63 µm, length of processes 28 µm.
Range of 10 specimens: central body diameter 50(60.1)77 µm, length of processes 25(27.0)31 µm.