Described by Hill and Wetherbee; type species Proteomonas sulcata (marine; Hill and Wetherbee 1986).

Only one strain has been sequenced (Marin et al. 1998; Deane et al. 2002; Hoef-Emden et al. 2002). Proteomonas sulcata was the first cryptophyte for which a dimorphism was reported (Hill and Wetherbee 1986). In molecular phylogenies inferred from nucleomorph SSU rDNA sequences, this strain seems to be related to the other two PE545-containing clades with free nucleomorphs (Guillardia/Hanusia and Geminigera/Plagioselmis/Teleaulax genus complex), whereas its position is not resolved in nuclear SSU rDNA phylogenies (Hoef-Emden et al. 2002).