Baltisphaeridium septatum, Cookson and Eisenack, 1967

Now Spiniferites. Originally Baltisphaeridium, subsequently (and now) Spiniferites, thirdly Hafniasphaera, fourthly Achomosphaera, fifthly Rivernookia.

Holotype: Cookson and Eisenack, 1967b, pl.42, fig.6
Locus typicus: Rivernook Member of Dilwyn Clay, Victoria, Australia
Stratum typicum: Late Paleocene

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Original description: [Cookson and Eisenack, 1967, p. 253]

Diagnosis:
Shell spherical, thin-walled with a closely and rather coarsely apparently granular surface and a variable number of radially arranged appendages which approximate in length to the radius of the shell. A "marginal zone" often present, given the impression that the shell is thick-walled, is, in fact, due to compression.

Original description:
The appendages vary in size, shape and structure. The majority narrow somewhat from a broadened base and divide distally into two or three straight or curved tapering branches with closed, pointed or minutely bifurcate tips. The larger appendages are typically hollow and septate throughout; in the finer to thread-like ones, on the contrary the degree of septation is often difficult to determine and their distal portions, at least, appear to be solid. A few of the appendages are unbranched. A pylome has been seen in a few specimens.

Dimensions:
Holotype: overall diameter c. 80 µm diameter of shell c. 57 µm, appendages 10 - 18 µm long.
Range: shell diameter c. 42 - 58 µm.