According to Solis-Marin (2003), this genus may belong to separate family.
Solís-Marín, FA. (2003). Systematics and phylogeny of the holothurian family Synallactidae (Bathyplotes, Mesothuria, Isistichopus fuscus, Deima validum, Paroriza prouhoi). Diss Abstr Int 65:109.