The subgenus Trigonia (Protrigonia) Guo, was proposed in 1985 to encompass T. yunnanensis (type species), T. gaytani and T. zlambachiensis. The generic name is preoccupied by Protrigonia Hampson, 1896, a monotypic genus of Lepidoptera. In August 2001, Repin defined the subgenus Trigonia (Primatrigonia), type species T. zlambachiensis, and in December 2001, Hautmann proposed the subgenus Trigonia (Modestella) based on the same type species. Eight years later, he realized that the name Modestella was preoccupied by Modestella Owen (in Casey, 1961), a terebratulide brachiopod, and he introduced the replacement name Modesticoncha for the junior homonym. Under such circumstances, Trigonia (Primatrigonia) Repin is rendered the valid name for this Triassic subgenus. In addition, in November 1981, Parnes proposed the mid-Jurassic subgenus Myophorella (Trigonellina). Since the genus Trigonellina was established earlier by Buckman (1907), for a terebratulide brachiopod, the name Parnesellina nom. nov. is proposed to replace the junior homonym.