Riding and Davey, 1989
From dinoflaj3
Riding, J.B. and Davey, R.J., 1989: Rotosphaeropsis thula (Davey 1982) comb. nov. and emend.: a dinoflagellate cyst from the Upper Jurassic-Lower Cretaceous of England. Journal of Micropalaeontology, v.8, no.1, p.109-112, pl.1.