Turbellarian taxonomic database
Rawlinson et al. (2011) (citation) remove the synonymy Faubel (1984) proposed for this genus to Prosthiostomum. They say "Poulter (1975) and Prudhoe (1985) support Kato’s (1938) original erection of the genus Amakusaplana, based on body shape, eye arrangement and, most importantly, the absence of a ventral sucker organ. We therefore recognize Amakusaplana as valid, based on these characters."
Litvaitis et al. (2019) (citation) (p. 18): "rather than recognizing a separate genus [Amakusaplana] based on highly variable traits, we here support Hyman (1959) (citation) and Faubel (1984) (citation), who proposed that the genus should be eliminated and synonymized with Prosthiostomum."