From Williams et al., 2017:

[Pithonella, Lorenz, 1902, p. 46. Emendations: Bignot and Lezaud, 1964, p.140; Villain, 1977, p.144; Masters and Scott, 1978, p.215; Keupp, 1987, p.39; Zügel, 1994, p.24.
Calcareous dinoflagellate genus (see Streng et al.,2004, p.483 and Elbrächter et al., 2008, p.1301, the latter noting that the cyst wall is pithonelloid and so a dinoflagellate affinity is questionable — see also below).

Tax. jr. syn.: Pirumella, by implication in Keupp (1981, p.44), who considered the "type species" of Pirumella, Pirumella edithvincentiae, to be a taxonomic junior synonym of Pithonella (now Pirumella) thayeri — however, Lentin and Williams (1993, p.517) retained Pirumella; Palinosphaera, by implication in Zügel (1994, p.17), who transferred the type of that genus to Pithonella — see under Palinosphaera for a full discussion; Cadosinella, according to Wendler et al. (2013, p.1098), although these authors did not propose any related species transfers; Calcisphaerula, according to Villain (1977, p.144) and Wendler et al. (2013, p.1098) (but see Elbrächter et al., 2008, p.1299); Andriella and Wallia, both according to
Wendler et al. (2013, p.1098). Keupp in Keupp and Mutterlose (1984) included in Pithonella forms of unknown affinity only; forms which are demonstrably dinoflagellates were included in Obliquipithonella and Orthopithonella. However, Willems (1995a, p.61) considered Pithonella to represent calcareous dinoflagellate cysts. Wendler et al. (2013, p.1098) considered that Pithonella has probable affiliation with dinoflagellates, although they confusingly listed the genus under both Calcitarcha (see Versteegh et al., 2009) and Division Dinoflagellata; for the present we
provisionally retain it as a dinoflagellate.

Type species: type: not designated; type species: Pithonella ovalis.]