Based on the unusual characteristics of the male pedipalp and male genital morphology, a new genus and new species of Gagrellinae harvestmen, Thunbergia gretae n. gen. n. sp. (male and female) from Shaanxi Province, China, is proposed. The tibia and tarsus of the pedipalp form elaborate palpal claws, resembling gaspipe pliers, probably used to grasp the legs or the pedipalps of the female during courtship. There is no comparable modification of the pedipalp in the female. The penis lacks wing or sac-like (saccate) elements normally present in Gagrellinae, and the penis base is markedly inflated to form a bulb-like structure harbouring the penis muscle. Two or three opisthosomal tergites are fused to the opisthosomal scute and, in combination, cause the male and female bodies to appear elongated and slender. Three further species belong to Thunbergia n. gen., namely Thunbergia grandis (Roewer 1912), Thunbergia wangi (Zhu & Song 1999) and Thunbergia zhui (Zhang & Zhang 2013). The genus Melanopa Thorell, 1889, to which the new species T. gretae n. sp. superficially seems to belong, is re-defined by revision of the type species from Burma (now Myanmar). With respect to courtship behaviour morphological interdependence of penial and of pedipalpal structures within Gagrellinae and Leiobuninae are addressed.