A parasite of the holothuroidean Chirodota laevis, A. sanguineum has a diminutive copulatory organ that has been difficult to place systematically (Hooge 2001). Aphanostoma sanguineum has separate male and female genital pores, although in some specimens the pores are positioned so closely together that they may be mistaken as a common genital pore, as was the case in Hooge's (2001) redescription of this species. 18S rDNA sequence data suggests a close relationship between A. sanguineum and members of the Actinoposthia (Hooge et al. 2002), and this relationship is further supported by A. sanguineum's possession of a penis comprising sclerotized needles (Fig. 10) rather than a muscular tube. We herein transfer A. sanguineum to the genus Pseudactinoposthia Dörjes 1968 (Actinoposthiidae Hooge, 2001), a rather heterogeneous group that is united in having a seminal bursa that is not equipped with a bursal nozzle