From Fensome et al., 2019:
Lingulodinium machaerophorum ssp. filiforme (Rossignol, 1964, p.91, pl.2, fig.13) Lentin and Williams, 1973, p.89. Holotype: Rossignol, 1964, pl.2, fig.13. Originally Baltisphaeridium machaerophorum var. filiforme (Appendix A), subsequently (and now) Lingulodinium machaerophorum subsp. filiforme. Age: Pleistocene.

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Original description: [Rossignol, 1964] (translated from French):

Baltisphaeridium machaerophorumn var. filiorme var. nov.
Pl. 2, fig. 13

Holotype: Ashdod 15/0 - 87-87.50 m. Blade A (AO 25.1×105).
Pleistocene.
The processes appear slightly more numerous; they are almost fliform, and their fineness makes them more flexible than those of the type species. The test surface is granular.
Dimensions: test: 42 μ
processes: 9 μ