From Fensome et al., 2019:

Membranosphaera, Samoilovitch in Samoilovitch and Mtchedlishvili, 1961, p.251.
Emendation: Drugg, 1967, p.29. The name Membranosphaera was originally used by Samoilovitch in Samoilovitch and Mtchedlishvili (1961, p.251) as the name of a "group". Lentin and Williams (1989, p.241) considered that the name Membranosphaera was validly published by Norris and Sarjeant (1965, p.40). However, Fensome et al. (1990, p.313) noted "... Samoilovitch and Mtchedlishvili (1961) assigned species directly to Membranosphaera, thus clearly indicating Membranosphaera to be equivalent to a genus. Since Lentin and Williams (1989) did not specify
which nomenclatural rule they were invoking, Williams et al. (1998, p.396) considered this generic name to have been validly published in Samoilovitch and Mtchedlishvili (1961)". Stover and Evitt (1978, p.263) and Fensome et al. (1990, p.313) included this genus in the acritarchs. Vozzhennikova in Lentin and Williams (1993, p.421) noted that Membranosphaera is a dinoflagellate cyst with an apical archeopyle.
Type: Samoilovitch and Mtchedlishvili, 1961, pl.83, figs.1a–d, as Membranosphaera maastrichtica.