Aspinothorax insolentis gen. et sp. n. is described from abyssal sites in the Laptev Sea (Arctic Ocean). The new genus is closely related to Styracothorax HUYS. The presence of a characteristic sexual dimorphism on endopod of the second leg of male Aspinothorax gen. n. demonstrates its phylogenetic relationship with Idyella (Idyanthinae: Tisbidae). As a consequence the harpacticoid family Styracothoracidae HUYS is rejected, and its only genus and species Styracothorax gladiator HUYS is transferred to the ldyanthinae together with the new genus. As a result of a re-evaluation of the family. Tisbidae, the family Porcellidiidae is rejected, because its members are closely related with the tisbid genera Sacodiscus and Scutellidium. Key-words: Aspinothorax insolentis gen. sp. n. Styracothoracidae, Tisbidae, Harpacticoida, Copepoda, phylogenetic systematics.