"With this reclassification, the genus Promacrostomum loses the type species and would only contain Promacrostomum palum Sluys, 1986 (Sluys, 1986), which was assigned to this genus because it, like M. paradoxum, has two female genital openings (while a genitointestinal duct was not observed by Sluys). While it seems likely that a molecular placement of this species would reveal that it belongs to Macrostomum, it is unclear whether it would group with any of the known representatives with this trait state or represent yet an additional independent origin. Given that the main characteristic of the genus Promacrostomum, namely the presence of two female genital openings, has several independent origins, we consider Promacrostomum unjustified and transfer its last remaining species from Promacrostomum to Macrostomum palum (Sluys, 1986)."